Agreed, IF properly managed its not anymore likely to kill an engine than other power adders like boost are, in fact due to the cooling side effect, arguably its safer adding another 100bhp with nitrous than it is adding another 100bhp with more boost.

But the ongoing cost of using the nitrous makes me personally a fan of other tuning methods first and then nitrous as just a top up, as you wouldnt want to rely on it for a full track session of 20 mins etc!

In track cars I would just treat it as a "push to pass" button where if I really get stuck behind someone who is slower over a lap than me but is quicker on the straights (happens a lot in clios, good lap times from the cornering but bad straightline pace) ignorant about moving over to let me pass then I can use it to get by and then carry on without it again.