Yes it is. Mostly — for me and in my forum anyway — personal chats have quite short TTL, one day and so. After that those channels are just unnecessary noise.
Most of users are using mobiles and then even 20 channels is really long list, especially when, for example, 15 of those are not alive.
Easiest solution for a user is ability to close and exit unnecessary personal chats. How easy that is technically… not a slightiest clue. But that option is needed.
Or chance to disable totally personal chats. That is an option too, because personal chat is somekind overlapping to (with? I really hate english prepositions 
) PMs. Chat is faster, though.