My father, who is well into his 70's had one of these calls.
He runs Linux (that he installs and maintains himself) and kept them talking for 50 minutes by playing dumb and being deliberately slow, then told then he had to go out, and could they ring back. They did, and he kept stringing them along for a further 40 minutes before he got bored and told them he ran Linux. Apparently they know some very rude words!
So who can beat 1 ½ hours
His logic was, well if I keep them talking they have less time to possibly scam one of my friends, and it will cost them both time and money to be on the phone to me that long.