I do not beleive the ASM's would become weaker over time due to pressure because the amount of pressure inside there is minimal
The only time I feel dropping it could occur is cleaning the skimmer. If the cup is dropped I do not beleive it would fair well however simply being carefull shoulf ensure it's not dropped.
I have a ASM G3 & a ER RC500 (was a 12-2) & I definantly like my ER more. The pumps are quieter & it's just built a LOT better!! My biggest complaint with my ASM is how difficult it is to remove the cup & lid due to salt/water/etc getting in there & making it very difficult to twist off. My ER is a older one & I beleive the newer ones have a much easier cup to temove. Mine is a 2 hand job & it takes a while to unscrew the union thingy they use. My lid just sits on there & is easy
If you want a needlwheel & are worried about longevity check out euro reef. They definantly cost a lot more due to better materials however for not a lot more money you can get a ER blem! My ER I purchased use which save be about 50%