Wanna do the maths?
Let's say x5. Around 8,700,000 xp needed
gen 1:
1000 xp per tick, 5000 if x5
8,700,000 : 5,000 : 60 = 29 hours
gen 16:
1450 xp per tick, 7250 if x5
8,700,000 : 7,250 : 60 = 20 hours
It's often less on battle, because you get 2 ticks for the first minute so you probably save up to an hour.