Q:

How important is a prompt reply in the freelance world?

When I am really overloaded with work, I don't have time to reply to new client's requests on estimations (how much will it cost, can you do these addons,...) as I simply cannot concentrate to produce a quality reply.
Often it takes up to 2 days before I reply them. And even after two days, I may reply by informing them that I am overloaded and that I will make a quality reply next week. No one has ever complained so far, but it does not mean that they did not have objections.
Now, what do you think of this? Am I being too rude or unprofessional? 
Shall I just have a sentence which I can paste which tells them that I will reply asap or next week? I hate machine-type replies. 

A:

If your reply is simply "I'm overloaded with work [... etc]", should it really take two days to send out?
As a (part-time) freelancer, I don't have the problem of being overloaded with freelance work (not yet!), but when coupled with all of my other responsibilities, it does get demanding. 
I will say though that when I'm on the other end and hire contractors, if I leave a message to say I'm interested in having work done, I typically expect a call back within 1-2 business days. 3 is pushing it, depending on the service. If that doesn't happen, I assume they are 
A) Unprofessional or 
B) Too busy to provide me quality service at this time. 
Time will tell if it's A or B. Eventually, if they do return my call, I still may ask for a quote from them if the work is still available, and may even go with them for this project or a future project. I understand some companies have busy seasons (landscape companies for example), and being busy myself I understand if small shops are overloaded at times.
Your response time would ring in right on the edge in my book. It would be a -1 though just to hear that you'd have to follow up with me next week. If the response is a 2-3 day period, I would expect the consult pretty much at that point in time, and not have to wait a business week just for a quote.
As a remedy, perhaps set some time aside during the day for following up with prospective clients. A 24 hour response time to touch base with them to schedule a future consult could go a long ways, and if everyone has the time right then and there you could do the consult then. The key word here (obviously) is schedule, a prompt reply to schedule a future meeting can keep your foot in that door, because rest assured that client is (at least should be) contacting other companies/freelancers that provide the same service, and don't want to wait a couple of days just for you to say your too busy and will call have time back next week. It's a microwave world now, coal burning ovens are a thing of the past. Calling and scheduling a meeting with them would at least hold them off from committing to another company until they've heard your offer. 
Of course, it could go the other way; if your reputation precedes you, they may even want to wait for you to have the time to do their work, because they've heard or know just what kind of work you produce.
That being said, if you're too busy to provide quality work, you're too busy to take on the client at this point in time. It would hurt to turn down a client, but you should at least follow up with them quickly, perhaps the time frame for completing the project does line up with your future schedule, and if it doesn't then you've made a great impression and they may contact you for further work (nothing wrong with being a backup). 

A:

I always reply within 24 (business) hours. Even if that reply is to let the client know I received their email and have been unable to provide the attention it deserves. I then provide a specific date to expect a reply. Generally that date is within one or two days, rarely (if ever) longer.
Prompt communication is imperative. Clients are generally more than willing to wait a bit if you ask them to. They tend to get upset and feel unimportant if you simply don't communicate.
I set aside the first hour or so of every working day for clerical matters - responding to emails, invoicing, tracking, etc. Then another hour in the afternoon for the same thing. Communication is as important in the freelance world as the actual work. 

I will add that I do not respond to emails, phone calls, text or other communications during non-working hours. For example, I have clients who will email me Friday night, Saturday morning, or Sunday evening. I never respond to those email until my next work day (Monday). EVER. As soon as you respond to someone during off-hours they assume your available during off-hours and will continue to expect replies in the future. Always use specific business hours to communicate with clients. Even if that means waiting two or three days (Friday to Monday) to respond.
The same holds true for general daily hours. I often work very late at night or very early morning. If I have an East coast client email me at 5 am and I happen to be working and see the email. I wait until at least 8 am my time (West coast) to respond. If a client calls or texts me at 10pm, I don't answer. They can leave a message and I'll get to it the next day. I'm not at their beckon call.
While it is very important to be prompt in communication, it is also important to set some boundaries with clients for your own peace of mind. If you fail to do this, you'll start feeling like you are "on-call" 24/7 and that begins to wear on anyone eventually. Freelancing isn't about being a slave to clients. It's about freedom. Be certain to protect that freedom in situations such as these.

