Awesome responses from everyone. I think for myself the speeds I have hit are fast enough and I don’t need to try any faster. Fwiw I have been riding a 1984 Trek 670, and I ride mainly in Redondo Beach which is a mix of flat and hills, and Palos Verdes which is all hilly. My top speed is coming down Crest Dr. which is a big climb to a dead end, there are always bikers at the top congregating and it’s fast sweeping corners you can take going full speed.
As for the comment about going fast downhill not really being a challenging, I am pedaling as hard as I can the whole way down with very little coasting at all. Obviously not as winded at the bottom as at the top though haha... it’s always windy here which definitely affects your speed, but when it’s still and flat-ish I definitely cruise in the low 20’s.