I would argue that they presided over this period rather than delivered it - big difference IMO.
Arguably, FG/Lab deserve the credit for being responsible for the general upward trend in the economy - but a different argument I guess, and OT.
Ultimately, you have hit the nail on the head though with the old historical FF/FG pro & anti treaty allegiances. That it can be more likely that a FF supporter will switch to SF over FG speaks volumes IMO.
It's potentially a fair comment and a discussion for another post as to who was responsible for the Celtic Tiger
As for a FF voter switching to SF, I can't speak for others but having had my house shook by IRA bombs, my desk blown to smithereens by IRA bombs and my wife threatened by IRA bank robbers and having watched SF politicians claim expenses despite never attending the House of Commons I for one would vote for anyone bar them