Actually he is all over the place on this. As I've read the bulk of AF's posts, his primary and most frequently stated position on velocity is that anything above being able to sit 91-92 doesn't matter. I'd say his second most consistent position is that command and secondary pitch quality matters more than velocity. I think they do matter more -- that is where Ks come from and a pitcher who throws 91-92 with good off-speed pitches and plus command can rack up a ton of Ks and do very well for himself.
I think the point that AF belabors and which colors his thinking is 'the right time' to spend and 'the right time' to offer deals longer than 2 years. To me, as long as you are not trying to snare a top 5 draft position and have ample salary cap space, ANY TIME is the right time to add talent and give the fans more wins... but, you have to add FA talent at positions of need where you aren't going to block promising prospects. I see no problem adding at 3B, but wouldn't add at other offensive positions. We are so far away from having 5 quality SP that I think we can add a FA SP (or 2) with no danger of blocking a future star pitcher. That still leaves 2 (or 3) positions for a young pitcher to grab in the rotation, and that is before the inevitable need for a 6th starter.
Any player is a risk. Diversification is the way to reduce risk to the norm. That means signing more than one or two quality FA between now and when we expect to enter the playoffs. Quality FA signings don't strike me as inherently very risky. We've been paying $11+ million/WAR for third tier FA and trade starting pitching. That's above average FA cost. The worst contract we signed in recent times was extending our own Ryan Howard. The worst pitcher deal/signing was trading for Garcia, with signing Burnett a close 2nd. Notably, he was retired when we paid a boatload of $ to sign him multi-year.