Generally the levels are with all cylinders extended, but your TC35 has around 9.8 gallons of fluid in its reservoir. If you fill it under any conditions so that the fluid is to the top of the full mark on the dipstick, you will never have to worry about not having enough fluid. I've had seeping leaks, dripping leaks, and flowing leaks, but rarely ever see the level below 1/2 gallon down. 1/2 gallon of fluid is a bunch when it is coming from a leak. If you are certain that all your plumbing connections are tight and the HST or main pump is not sucking air somewhere (look for bubbles or foaming in the reservoir) then I'd say you should not have to worry about fluid levels. Clogged filters and air leaks are a lot more likely than having low fluid cause a problem in my estimation.
