1st off Hi Sue
I have several antenna analyzer / VNAs , MFJ-269 , Sark 110 , and a MiniVNA Pro .
I keep all inputs covered with my calibration loads , either a 50 ohm load , short or open - probably in that order for effectiveness .
I started doing that after repairing several RF test gear and overloaded inputs MFJ 259s , TimeWave TZ-900 etc.
TimeWave is a friend of mine , club member and we talked about that , and ever since - capped all inputs .