I've never built wheels before - I like to try it. So I've been playing with the online spoke length calculators, looking at some of the hubs I have and some rims I'd like to possibly relace them with. I've noticed that most of the time the front spoke length and the rear spoke lengths are with 1mm of each other - for example, 299 on the front and 297 and 299 on the rear. Can I simply use 298mm spokes in this case? Same with a 650B rim I've been looking at with Campy hubs: 281 front, and 280 and 279 rear -> use 280mm all around? Otherwise I'm buying 18 of the shorter ones and 54 of the longer ones.
(Sorry if this is a basic question. Maybe I should take some wheels apart and measure the spokes?)