An older client of us was so kind giving me a package of Technidol to develop my Technical Pan with. Only this package is like 20 yrs old
I am still using old Technidol and it works as well as ever. I am not sure of the age - it is a liquid packaged in little foil pouches that have the shape of a bottle printed on them.
All the liquid Technidol that I had that was in little round plastic vials went bad quite a while ago.
Previous to all that, Technidol was supplied as a powder. I don't have any, but I don't remember having any that went bad.
The developing agent in Technidol is phenidone and phenidone turns brown when it expires. If the Technidol is clear/uncolored then it is probably good. Before doing the whole roll you may want to snip a bit of the film leader and put it in the developer in the light and see that it turns black(ish) in about 1/2 the recommended developing time.
If you have some phenidone and sulfite then you can make POTA which works acceptably with TechPan. Don't bother with HC110 or Rodinal - there are people who claim this works but there are also people who like rap music and eating at McDonalds. TechPan is the Beethoven 5th piano concerto of film, the prime rib of imaging, don't spoil it.