we don't even know if Bitcoin will last, in the end (i e over an extended period of time of, say, more than 20 or 30 years and thus amounting to at least 1-2 asset class cycles).

So, yes, your rather cautious approach is sensible, actually nothing more than simply good money management and therefore the right way of doing it. Yes, absolutely, let us enjoy while it lasts and be even more happy if it lasts a little loger -- or really lasts ;)