In reply to G3NYY:
M3 stations have been on the air for more than ten years without
attempting to upgrade!
If the Foundation Licence (10 watts, operation only in UK etc) is sufficient for you, there should be no compulsion to upgrade. There may be good reasons for the time factor - for Foundation stations that do intend to upgrade.
For instance Jimmy was M3EYP for nearly 7 years, rejecting all intermediate courses because he was prioritising his school studies. I know some saw that as an ‘excuse’, but it was genuine! With A Levels out of the way, he did his Intermediate, and almost immediately enrolled on the Full, which he got 7 months later.
Any imposition of time limits for the licensing structure would have rendered such progress impossible.
I am sure that there are indeed some Foundation stations who exceed their 10w power limit. I am sure that most don’t.
I am also sure that there are Full stations that exceed their 400w power limit. I am sure that most don’t.