Left Ctrl key stopped working totally

Solution 1:

I'd be surprised if normal wear & tear would be able to do that in just 30 months or so. I only retired my similar keyboard after about 7 years, when I could no longer read the letters, I'd worn them off.

I'd try tapping the offending keys with greater than usual force, see if something crispy is stuck underneath. After that, I've heard of people having success actually running keyboards under the tap - so long as they are given plenty of time to thoroughly dry out afterwards, though I've never done it myself.
Wouldn't try it with a wireless keyboard, but wired might just be fine.

Late, late edit
After giving one of those keyboards a drink of water accidentally, I wouldn't recommend it as a cleaning method. Killed it stone dead. The rinse under the tap method is apparently only appropriate to much older keyboards from the 90s.
They do seem to respond well to a squirt of contact cleaner, though.