Free citizen, you give very good advice. I've been using XTOL since it first came out. I replenish when using larger tanks, works great. I have several sizes of bottles the stock is always kept full.
When I use my Jobo processor I use stock XTOL one shot, I worry about oxidization with all the swishing about.

True story, we moved to a new house several years back. Last year I found a bottle of stock XTOL that had gotten put away in a closet of household supplies. The bottle was 11 years old, looked like a pale beer. It was stored in an absolutely full, air squeezed out PET soda bottle. I was getting ready to pour down the drain. I thought I will never get another chance, I developed a roll of 120 film, gave it an extra 20% development time. Negatives turned out fine. I couldn't believe it.
I always use purified water for mixing. I use XTOL that has been stored up to a year no problem. The keys are pure water and no air.
Amazing developer.
Best Regards Mike