Yea, it's a shame they can't figure out a way to simultaneously put them at (say) 105 (their new home) *AND* on 119 or 110 - that way, you could see them for a little while... when the free preview is over, do one of two things:
1) For a while, leave a 'message screen' kind of thing (from 110/119) saying 'this free preview of XYZ locals is now over, contact us to subscribe, blah blah blah
2) Just delete them from 110 / 119 entirely.
I'm sure there's some reason why this isn't done (no xponder space on 110 or 119?), but if the channel numbering is a problem then just put these 'previews on the wrong bird' channels on some funny high-up numbers instead of the numbers where they would go.