Parts are hard to get for everything, that's to be expected these days, Id imagine since most/all of these lifts are manufactured out of the country Nifty isn't the only one. When comparing other manufacturers machines part wait times are probably comparable, hopefully I won't need to find out any time in the near future.
As far as being in the weather, they don't advertise you can leave the machine outside, the Dinolift on the other hand is supposed to be weather tight. I keep my SD64 inside when not it use, so far so good. Also I have used it in heavy rain and wind without an issue.