Hi,
as we are all no TT employees we cannot give you any further answer to that question as we don't know about TT's internal policy.
And I doubt that any TT employee will answer you this question with the complete truth as no company will ever publish their internal policy.
We'll just have to take it as it is, maybe ask TT for some other ways of promotion for users needing all those map updates or having many devices in their possession for getting discounts. Maybe if Garmin and other brands gain some market share from TT they'll give us Europeans lifetime maps as well but I fear that'll take some time.
Regards
Lars.