The Black Diamond QC Lab have done some testing on old ropes and got maybe not surprising but still scary results.
The rope broke already at a force of 6 kN which equals what a 5mm nylon cord can handle according to (Climbing Gear Strength Ratings). The same page lists 9 kN as the theoretical max. force possible in a climbing fall.
Keep that in mind when spring arrives and you take out your old rope again.