Larger gaps between checkups - dangerous?

[Jackalesque]

OK, so I'm now on tray 6 out of 31 of Invisalign (bottom teeth only at the moment, I start the top teeth on tray 12).

My dentist is in Cardiff and I'm moving to Edinburgh this month, which is over 400 miles away So to be accommodating to this, he's agreed with me to give checkups about every 3-4 months which is less often than recommended.

I'm worried that because of this, I won't know if my teeth aren't moving correctly until the checkups and that's a lot of time wasted. In your experiences, have your teeth generally been moving as prescribed without intervention at checkups? I don't mind if they're not *quite* there at the end and I need new impressions taken, as long as it's quite close to the end result.

I asked him at my last checkup whether he thinks it's working so far, which is hard to tell after only 5 trays, but he told me that the trays won't fit if the previous movements didn't happen correctly. It makes sense in theory, but how true is this?

Thanks for all your help