After finishing thing v2, did you get rid of thing v1?
This is one of my pet peeves: the inability to actually deprecate the "old" version of something is always so hard. There are always users who don't want to switch. Or that obscure feature you don't want to support in v2 that keeps users from switching. Or my favorite: a general suspicious attitude against all new software.
I'm currently writing internal software for a high tech Corp. It's an even worse situation than writing paid software for actual customers.
Did you manage to deprecate it? Even to delete the code entirely?