Yong Heng oil changes

i got a bottle of royal purple when i bought the pump over a year ago .. havent changed it yet . i should simply to get any factory gunk out, but compressor oil isnt critical to change, its not like vehical oil that gets contaminated with combustion and 'cut' with solvent like fuel ... just make sure its at the proper level .. that 'is' critical, and after that first change to get the manufacturing grime out id say its good for the life of the pump ...
 
I used royal purple like many but the compressor sounded strained because it is so thick. I switched to just normal good quality transmission fluid which is a lot thinner and it sounds a lot better. I know I don’t really need to change it much but i changed it twice because it doesn’t cost me a dime since the those are left over for a car I already sold.