of course there will be lag...
pay a second to how many people are actually online at the moment the release pops up..
even if you do it straight after the maintenance there'll be lag if only for the sole fact that it'll shoot up from like 200 people online to 600 people online (tho it's easier hitting up more cause I think we've seen it be 800 something once already)
and if you have a slow connection or other obligations on that day, would it really matter that much if you have it a few hours earlier? I mean, get up an hour earlier the next day.. problem solved... you won't hear me complain, by the time the release hits cave I'll be OMW home and then I need to go to bed cause I have to get up at 5.30am to go to work only to get home at 5.15pm meaning I'm about 100% sure to miss the release... will I hate it? no cause people will breed the eggs and I'll just grab one from the abandoned pile so the cave won't get blocked PLUS those poor babies don't need to die