I also am aging and snap reflex are not what they once were. I have recently started trying lost sectors solo legendary and it really depends heavily on your build and which lost sector it is. Ignore the youtube videos "60 second lost sector farm" cos that just aint gonna happen take your time at first and you will slowly get faster and faster. Consider your build for champions and shielded enemies also some are easier than others i.e. last week the cabal lost sectors in the EDZ were pretty easy and I could get through in under five mins or so but the fallen ones on the moon were just a pain in the -blam!- with champion servitors and it would take me 10-15 mins per run, I only did a couple of runs and then couldn't be assed with those servitors anymore. Just keep at it and you will succeed. Eyes up guardian.