If we speak about recent times, then I would say in 2008 in the middle of recession (like I have been advocating since the begining here on pprune).
And saying "good time" is a bit too much I beleive, giving a bit more chances would be more accurate.
During 2003/2004, it was a good time to train to, when everything was at its lowest.
If you speak about time during the year, that's different.
If you want to be instructor, you should finish your training during the winter to be able to start with the spring.
Too many instructor student found themselves ready at the end of the summer with no job, they gave up afterwards, timing can be tricky sometimes.
I would wait a bit, save money. If we get in an other recession next year, I would start my training at that time, because I beleive recession always stop. Right now we are, I believe, just before a recession, or at least big economic problems.
Wait to be in the middle of it to start. In addition your training will be cheaper and the instructor more available (I am not saying this is booming right now...).