Perhaps I'm listening to too many older people. In fact in recent years the US Congress has been getting older!
Statistics produced by the Congressional Research Service show the average age of members at the beginning of each Congress. In 1983 the average age was 47.0 - at the start of the 111th Congress (just a year ago) the average had risen to 58.2 years, making this the oldest Congress on record.
Detailed figures - and graphs for the whole of Congressional History can be accessed here.