Is it though? England did lose Canada to home-rule. In fact, I contend that a major reason why a newly independent (but also broke and fledgling) Canada was not annexed by the US was mainly because of the American preoccupation with civil war and Reconstruction, and the diplomatic efforts of John A. Macdonald.
In another thread, I also made an argument for another major mitigating factor with respect to Americas, namely, the native populations were wiped out by old-world diseases which prevented local rebellions from succeeding and allowed Europeans to establish large population centers.
To which the existence of British colonies in Canada after 1776 is kind of a direct rejoinder, right? The eventual loss of those colonies is irrelevant to the point that you can’t explain the American revolution as being an inevitable consequence of remoteness.
If the territory is fully pacified with no significant resistance and/or it's run by dedicated loyalists with plentiful local resources the limit doesn't apply.
Basically an empire can only retain territory against an active threat or resistance within certain limits. If there is no active threat, or the threat is too minor to be a concern, the territory can be considered stable and fully colonised.