Not to start a war over the issue, but I have to either disagree or qualify items that Ian raises. I decap and seat all my primers using my press and find it just as easy to feel a loose primer pocket with the press as with a handheld unit. I've been reloading both pistol and rifle ammo since 1975 and have only had one blown primer - 9mm - and it wasn't because of a loose primer pocket - a strange overpressure situation that was likely caused by the bullet getting pushed further back into the case while feeding from the magazine. I think this may have been a situation where the case was just enough out of spec not to crimp tightly enough to prevent bullet setback. I do use a hand held primer seater when loading rifle rounds for maximum accuracy.
I stopped measuring pistol cases for overall length a long time ago. Mostly because I use a taper crimp die and find that the overall length doesn't seem to matter as much with that crimp die as it does with the "do it all seater/crimp die" which generally uses a roll crimp. At any rate, your pistol cases are likely to split long before they'll need a trim. I will qualify this statement with a recommendation to measure case length if your prone to shoot maximum loads, especially in revolvers, since you can seat a bullet too deep with a lengthened case, e.g. case gets longer and the bullet seats deeper into the case - see my blown primer incident.
Rifle rounds, again, are a different animal. I find that I can get away with at least one reload without having to trim the case and sometimes two. There's just something about the bottle neck in a rifle case that lends itself to neck stretching - especially if you full length resize a case. With bolt action rifles I prefer to neck size only (you've got to make sure the fired case comes from the same rifle and used for this rifle only for this to work properly, and it only applies to bolt-actions and not auto-loaders) as this seems to minimize case stretch and seems to help in that quest for maximum accuracy.
I find that reloading your own saves money over the long haul, allows you to customize loads for specific results - like light practice rounds, and can be relaxing. On top of those reasons, there's something satisfying about "rolling" one's own ammo and successfully shooting it.
