The service time is a function partially of the system model and partially of the warranty you have.  If it's a next-business-day warranty (applies to Latitude, Precision, Optiplex) and you have onsite service, it should be rapid response. If it's a consumer-grade system (Inspiron, Vostro), with depot service, you may be waiting a while - these aren't backed by the same level of support as the business models are. All you can do is call and ask -- if the system has to be replaced due to unavailability of the parts, you'll get whatever refurbished system they have that's closest in specification to your current system.  
A little more than 3 years into my 4 year warranty the motherboard has died on my laptop. The part either exists or it doesn't and that should be easy to determine but Dell can't seem to do this. All I know now is that the part hasn't been located and is estimated to be shipped in 2 weeks. How can you estimate a shipping date for a part you can't find? I paid a lot for this laptop and a lot for a warranty that led me to believe that the extra money I was spending would guarantee me better support. Losing the use of my laptop is expensive for me. Very expensive. It's so expensive that I've had to purchase another laptop because I can't get an answer from Dell as to when I might expect to have resolution.  My questions these. If the spare parts can't be located, is there a maximum time I will have to wait before a replacement for the laptop is sent to me? Would this replacement be comparable to the one I lost to hardware failure? Would the remainder of my expensive warranty apply to this replacement laptop? Thank you.
Max time under warranty to wait for spare parts?