Quite an emotional subject, and nobody likes to see a once proud warship in the knackers yard; but, this happens to 99.9% of ships. The only argument is whether keeping the Invincible (and the Ak Royal) in service would be viable and economic. The alternative (in the Libyan war) of staging RAF warplanes from Southern Italy has proven both extremely expensive and limiting in operational terms, compared to keeping just one of the Invicibles in service with remaining Harriers off the Libyan coast.
In many ways this is symptomatic of the malaise affecting the U.K. armed forces: over extended in multiple combat zones, short of equipment and manpower, facing further cuts and redundancies, and with low morale. Why the U.K. is expending scant resources in Libya is a question we should consider. The USA is underwriting the NATO operation by providing non combat support, but there are neighbours of Libya, particularly Egypt who are keeping well out of the civil war. Apart from France and Italy, I'm not aware of other NATO countries committing in the same way as the U.K.
Maybe the armed forces of Denmark are small, but in Libya we commiting in the highest end by percentage.
About the Invincible I think it's awkward to take a vessel out before the replacement is build and commisioned