retrolefty:
I would never select power components that had to operate closer then say 75-80% of their maximum rating to allow for some 'headroom' and possible future increase loads.
Yep.
I bought hundreds of electronic components on eBay, including quite a few of those DC converter boards, a lot of power LEDs, etc. After the first few items that were constantly too hot to touch (some 3W LEDs IIRC) I started running everything at about half advertised power. I've never had a problem since then.
If you design accordingly you won't be disappointed.
retrolefty:
Device maximum specifications are almost always stated optimistically...
My experience is that they're absolute maximums for the device, with best possible heatsinks under ideal conditions. Not a good idea for long term use.