Hot swapping 16tb to 24tb - 1522+

Hey all. I need more space. I'm trying to hold out for the 1825. I currently have my DS1522+ filled with 4x16 and 1x20 TB drives. Plan is to swap out the 16's for 24's. Buy the 1825 when it's out and continue.

Is hot swapping still the best way? Any safer method to hot swapping? Any tips that aren't widely known or not talked about?

How long of a rebuild time am I looking at?