I think yeast loss some % of vitality per week in the fridge, either 5 or 10 percent. This means after 2 months, assuming 10%, your yeast is almost 20% of what you had at the start (technically it is more, but simple math at the moment). Anyhow, your method of decanting and pitching on a fresh set of wort is the right thing to do. you should see fermentation like you would with any starter. At the most basic, a hydrometer test at the end (assuming you stirplate) should show a drop in gravity.
*** not so simple math... If I understand it right, you loss 10% vitality, which means you keep 90%, or .9 so .9^8 (yes 8th power for 8 weeks - 90% of 90% of 90%.... for 8 times) which gets closer to .43%... or 2/5 of whatever it was when you put it in the fridge. This all assumes that the yeast didn't get contaminated and such.