Shell Tellus 22 and Mobil DTE 11 are the same exact oils.

SHELL TELLUS OIL S2 V 22 is an ISO 22 weight oil and any brand of ISO 22 hydraulic oil will work fine. When you change it. You can also go with a heavier oil such as ISO 32 which is easier to find at auto parts and farm supply stores.

I have never heard of changing hydraulic oil after X number of hours. For it never goes bad unless it is heated beyond 350 degrees for an extended period of time. We have ran heavy equipment almost 24/7 in mining operations for ten to twelve years and never changed the hydraulic oil in them. Filters yes. But never the oil.