Should I hold back some ideas for after my PhD? I guess this a question about 'career pacing'. I am currently a first-year grad student studying for a PhD in Aerospace Engineering at a research university in the US. Even though I have only been studying this field for about 5 months, I am already starting to get quite a few ideas about interesting potential avenues for research. For example, possible numerical simulations or experiments that could be done.
I am thinking about pursuing an academic career post-PhD, so my question is: would it make sense for me to keep some of these ideas 'in reserve' for a possible post-doc or tenure track position? If I have one or more really 'great' ideas, when is the best time to pull those out of the bag? Now, during the PhD, or save them for later?
What I'm thinking is: if I pull out my best ideas now, it might be less clear whether they were really my ideas or my PI's; however, if I wait, then someone else might have similar ideas and beat me to it (i.e. publish or perish).
To look at it in another way: when is the optimal time during an academic career to fire off your 'biggest impact' ideas (if there is such a thing)? If I have more 'promising' ideas than I think I can work on during the PhD, would it make sense then to keep some in reserve?
I don't see a point in holding back ideas on purpose, at least not for a longer time.
If you are doing well in research, you will generally have more interesting ideas than you have time to pursue.  And you will keep having new ideas all the time. So there won't be a time when you will have ample of time, but be in desperate need of a great project.
So you should work now on the best ideas you have now: First, people will judge you by your best work and best ideas. If you work on more exciting ideas now, you will be more likely to secure good postdoc positions later. And if you have a fair advisor, they will clearly credit you with those ideas (e.g. in recommendation letters).  So you win by working on your best ideas now.  Second, your best ideas now might be outdated in a few years time, or your interests might shift, or you might have even better and more timely ideas at that time, so there is not much point in saving those ideas.  Third, someone else might have the same idea and publish a result on it in the meantime, making your ideas not new any more.  And finally, even if you don't have the time to work out all ideas fully yourself, it can make sense to share them with colleagues: Maybe they get excited by the ideas and collaborate with you on them, increasing your scientific output.
Finally, what if you will not have good ideas any more in the future? Well, then very likely your chances to secure a permanent position in research are slim, and having kept your old ideas will not save you.