I disagree. (I know, predictable.)
You wait until you don't have an LT to get one. Otherwise, you have invested way too much draft capital in a position (RT or G) for who knows how long where a lesser pick is going to do just as well. And Long get pissed off because his successor is already on the team and he feels unvalued. I wouldn't be surprised if he asked for his release in that circumstance. Saffold didn't, but only because he only had one year left on his contract anyway.
If talent is roughly equal, you take the guy you don't have over the guy you have. To me, that's the no brainer.
Plus with most of the OT crowd wanting Robinson, his rawness still scares me.