heating and tumbling but still takes forever to dry

Trying to troubleshoot mr dryer, but not experienced with appliance repair. My secondhand dryer was working fine until about a month ago. It seem to function properly (turns on, gets hot, tumbles freely, etc.) But it has slowly reached a point at which even small loads take well over an hour to dry and sometimes more than two hours. I recently dismantled it to clean the interior and check for blockages. I found none and evrything inside seemed intact. Performance still has not improved. I have not checked for continuity at any points as of yet, since i do not currently have the proper tools.
Am I missing something obvious, or is electric diagnosis the next step?
If so, other than reading the sticky about continuty, is there any other resource for determing a fault?
I appreciate any advice and realize you must tire of novices ; )
Also pardon the typos. Sending this from my phone with tiny keyboard.

Given the age of your machine I would say you need to check the heating coild for continuity. If it is ok, and you are sure the interior venting system is not clogged (check where the filter goes) then you might try changing out the thermostat.

Incidentally, this is a Frigidaire model sold under the GE label.

Took me awhile to find my way back here. I did want to say thanks for the reply and the advice. After thorough testing of my dryer, I discovered the old bugger works just fine. The ductwork in my house was the cause. For some unknown reason the duct goes from the dryer, into the wall, takes a 90 degree turn straight up TWO STORIES before another 90 degre turn in the attic and out the roof. Needless to say, there were several blockages that prevented the dryer exhause from working properly. Go figure.

Now I am searching for a workaround for the dryer exhaust that isn’t a complete fire trap.

Well good, glad you got that figured out. See what you can do about the venting.

Thanks for the update.