Consider the various components:
CPU ==> fine at those temps (with system off)
Graphics card ==> fine at those temps (with system off)
Memory modules ==> fine at those temps (with system off)
Motherboard ==> fine at those temps (with system off)
Power supply ==> fine at those temps (with system off)
Hard drives ==> Probably okay as long as the max temp is 150. For example, Western Digital's drives have non-operating specifications for their hard drives of up to 70° C (158° F), so in theory a temperature in the 140-150 range is okay ... although it's clearly not ideal -- and I would definitely let the system cool off for a LONG time after it was heated to those levels before powering it on (at least a couple hours).
Optical drives ==> Should be okay at those temps, but I can't find detailed environmental specs for the most common units (but I'd expect they can easily withstand the same levels as hard drives)
The solder on the boards is NOT a consideration ==> typical 60/40 solder flows at about 190° C (374° F) ... so you're nowhere close to that as an issue.
Bottom line: 140° F is clearly okay; 150° F SHOULD be okay, but is a bit more worrisome. As long as the temps are controlled so they stay closer to the 140 point and do NOT exceed 150 a system should be fine.