Regarding the rim, 5-6,000 miles IS a good innings... but still, the rim has not worn down to the indicator groove at all and still cracked. My Birdy front rim is now on 11,000km and worn out, about to be replaced; the rear rim (with indicator groove) is still like new (since I don't use rear brakes except in emergencies).
Regarding the frame cracking, while the Vitesse aluminium frame was changed to address the stress cracking problem, the Speed frame was not changed. And the Mu has inherited the same weakness (Steveroot's cracked frame is clear evidence of this).
Then there is the sorry saga of the (Revolve?) stempost breaking off, the one with the internal latch with no safety backup. Dahon put bandaids for all they are worth on that POS but it eventually led to a recall, but not before a complaint was lodged with the relevant safety authority.
So while I think that Dahons are very nice bikes indeed, clearly the company is not managed by David Hon any more, at least not like in the beginning, and there isn't an engineer in sight. They get the nice-looking stuff right for sure, but the nitty-gritty important details are lost in a frenzy of marketing.
Finally, it is a long-known issue that Dahon spares are very hard to get hold of, at least the less-common ones such as front hubs.