Ciao
The smaller the size of the snapshot file, the better.
In the past, I have had problems with VMs with snapshots up to several hundred GBs.
I don't think there is a maximum size (Obviously it should never get bigger than the size of the VM you created the disk for)
But the snapshot is not a backup and the less time they are kept active the better (talking about VM server environments, for VDI the question is slightly different)
