Two years I'd say 69 for the Harrier - 71 for the Viggen.
And i think we were finding new and inspired ways of getting Harriers to fall out of the sky for much of that time.
No Falklands fast jets?
You can answer this a few ways.
1) Keep the Buccs and Phantoms and the Ark Royal going on the cost it took to develop the Harrier!!
2) Build Sea Viggens!
3) So what - no task force.. Maybe a submarine only blockage of Argentine would have been worked with time.