I guess long term will be reliant on use and weight and floor type.
I find the problem with risers, especially on floating floors, is that the legs move due to the point loading, that then means over time that the wall/tile seal can be compromised. Added to that, due to the same point loading but on the tray itself, if it is being used a lot with a more heavier user then the tray can actually crack. Seen that a few times too.
Any tray, in my experience, should always be supported over the majority of it's footprint, that will minimise any longer term issues of cracking or seal problems