Is it reasonable to put all printers to another subnet?

Is it reasonable to create complexity fo the purpose of simplifying ip address management? Not in my opinion. Putting the printers and AP's on another subnet means having to route traffic between the printer/AP subnet and the main production subnet. It also means having to create a different DHCP ip address pool for AP clients. It also means having to create VLAN's on your switches for each subnet and having to configure your router to route traffic between both subnets. That sounds like a lot of work and complexity relative to the problem.

If you need to better manage the ip address assignment of the printers then my recommendation would be to create DHCP reservations for the printers in your current DHCP ip address pool.

you could do it that way if you wanted. i'm not sure it's worth the hassle. if everything is going DHCP, then let the printers get their addresses via DHCP, too.

and if you give them proper names in the network configuration, then they will show up in DNS with those names. then you don't have to care about what IP address they get because they will be addressable via DNS names.

Yes, It's perfectly reasonable to separate them out for security. Especially if you want to utilize Internet/ wireless printing.