I install a rebuilt 1918 engine with adjustable valves in my 15 T. I've put maybe 200 miles on her. Adjusted the bands a few times almost no lint in the screen the last time. At what point should I think about checking the valve clearances?
I have put 4000+ miles on Betsy, my 1924 cut-off touring, so far without any valve adjustment.
OT, but on my old 1969 Plymouth Valiant with a slant six, I could tell it was time to adjust the valves when the engine started idling roughly.
More OT, I have yet to need an adjustment of the valves on my daily driver 2007 Honda Element after 118,000 miles.
If you have a good set of lifters and the valves are correctly set when ground, you should not need to adjust the clearance again. The valiant has a lot more parts in the valve system to wear and get out of adjustment. In the T there is only the cam to lifter space and the lifter to valve clearance and the wear on the cam bearings. On the Valiant, you have the cam and it's bearings, the cam to lifter, the lifter to push rod, the push rod to rocker arm, the rocker arm bearings, and the rocker to valve. The original T lifters were not adjustable and only needed to ground to fit when the valves were ground. Same should hold true for adjustable lifters if the lifters are good.
a compression check will tell if you need a valve adjustment.....or possibly rings
The Valiant also had much stronger valve springs than a T and was designed to run on leaded gas.
After years, of running on unleaded gas, the exhaust valves were slowly pounding their way into the cylinder head, which would eventually use up all of the lash and require loosening up the adjusters to restore the proper lash.
With its weak sister valve springs, whether a T would suffer this wear mode could (and probably will) be debated.
Compression won't always tell if you you need an adjustment. I just repaired a motor that had 50# while cranking but still would not run well after owner had done a valve job. Valves were seated well and adjusted correctly but the guides were very sloppy. Reamed the guides and oversized valves and it runs great.