Upgrade 3070 to 4070?

I have two 3080's and a 3070. The 3070 is a champ but is getting on about 3mil clicks and I have the opportunity to buy a low mileage 4070. Max usage is about 40k a month. I see some parts are shared like developer and toner (which is helpful and cost efficient ) but not drums.
I am off contract on all machines and either do my own maint or I have a local indy tech who is very good for when I get in over my head.

Any reasons I shouldn't move up to a 40 series? I saw some mention online about issues but thought I'd ask here.

Thanks in advance!

 

On the flip side, why do you feel the need to upgrade to the 40 series? 3mil clicks is not that much and sounds like you're pretty set for maintaining it. Seems like spending money for no real reason.