I'd sit out and wait to see what the Watch 5 offers (and what Samsung with throw in as an incentive) if you're in no rush. Be a win win situation - see what it offers and go for it, or pick up the Watch 4 for cheaper as they'll drop the prices soon as 5's on pre-orders.
Personally though I've had the 4 Classic since launch day and happy with it. Battery life for me is around 3 days on a full charge.
I read somewhere that the watch5 is only going to have like 30mAh more than the watch 4 which would probably give it a few more hours. That's if the software and hardware of the watch5 aren't more battery consuming. Personally I'd wait and see the full specs and difference between the two and prices and base my decision on that