If one leaves the workforce for some period of time, upon re-entering the workforce, one is sure to get asked for references for that first job back in. Is it better to provide older references from previous similar technical work, or personal references that are recent? Is it better to stick to purely professional ones, even though they may not be recent?
Many references are requested for purely professional reasons: what kind of worker you were, how timely you were with your work, how you reacted with work stress, how competent you were in your work -- work related questions. A personal reference can refer to what kind of person you are, but won't know what kind of work you do.
So yes, you're going to want older references, if that's all you have. If you've kept in contact with them that will have helped, because they'll remember you (and hopefully remember your work). Contact your potential references and let them know they may be contacted, and make sure they are willing to be references.
It won't hurt to have some contact information for more current personal references too, and offer them as well.
Hmm, I'd say being asked to provide references is something that happens regardless of whether or not you've been out of work or not. I had one of my references tell me 'casually' that when people ask for references, it should be no more than 3 years back. Or was it 5 years? Either way, it felt like a very constrained time period.
As for personal vs. professional, they don't specify? I've always been asked for managerial references, and restrictions have included that they can't be family members. In your case, I'd say definitely use ones that you're most comfy with (call/email ahead to make sure they'd still be willing to be used as references), but otherwise, I'd say mix up 1 or 2 professional ones with 1 or 2 personal ones. If looking for 3, I'd say prioritize the professional ones (so 2 pro, 1 personal in this case) since they should bear more weight.