I'm basically re-writing a question that has been asked before about not having a letter from one's current institution to see if anyone has any additional thoughts or advice.
I'm in my second year at my current institution and I love my job. However, for family/location reasons (and to try for a bit of an "upgrade" in terms of teaching load and institutional resources), I am applying for a job this year. Just one, because I love my current job, but there is one job this year that would be better for me and my family.
I asked my old letter-writers for letters again and they all agreed, but one of them pointed out that their letter was going to be kind of old (from graduate school, and I did a postdoc in between.) The good thing is that the others are with faculty I'm still working with on some projects, but this third letter is a bit dated.
Meanwhile, I have been doing quite well in my current position. The only problem is that I can't imagine telling any of them that I'm applying for another position, let alone asking them for a letter. Our department is small and losing anyone would be a real blow (even assuming the tenure line gets replaced.) I'm not bragging when I say they'd freak out if they knew I was even applying. I'd be scared to ask someone in another department, too; word gets around, and I also don't want to be thought of as someone who's totally disloyal (I realize how hypocritical that sounds, but I do feel intensely loyal to my institution; I just also feel an intense pull to this particular location of the country.)
For now I'm going to stick to the three letters that I have, but this issue might come up again (assuming I don't get the job this year). I'm going to keep aiming for schools in that general location every few years, depending on what opens up, and in recent years it's been about 1 suitable position in the region per year. My old letters will get even older in the meantime. Anyone have any tips of who to cultivate letter writers down the line? Faculty at other schools who I see at conferences? Faculty at my school in another department? Retired faculty from my department (who know me)? People who have reviewed my papers a few times before? And should these candidate letter-writers all be senior compared to me? I just don't know who to ask or, quite frankly, how to make outside connections that are strong enough to be letter-worthy.