I think the age gap is the hard part. I'm 9 years younger, so I do feel guilty that he's planning to work longer. In order to get past that guilt, I've created all of these artificial goals for myself that would "make me feel better" & ready to leave. I've BLOWN past all of those goals. He's supportive of me making this change, so the majority of this is on me & my own feelings on the age gap.
I don't have any answers for you on this, largely because I'm living it myself, but in reverse--I'm 11 years older than DH (I'm 52, he's 41) and I'm the one who would quit tomorrow if I could get over the mental hurdles; on his best day, he loves his job, and on his worst, he tolerates it, while I tolerate mine on my best days and want to curl up in a ball on my worst. ;-) But maybe you'll find a thread of something in my story that will be of some assistance.
DH and I have had the when-can-Zoot-quit conversation many times--and he has assured me every time that I can quit tomorrow if I want to. Our LNW is roughly $800K in retirement funds and $100K in taxable, with another $250K in home equity. We can live on his salary, comfortably but not lavishly, but our savings rate would take a big hit without my salary. Every time I think about quitting, though, I am struck with guilt--I somehow can't conscience leaving work while he's still working. "You've paid your dues for a decade longer than I have," he will tell me. "It's OK if you want to go ahead and quit--you don't need to work just because I am." And yet I still am.
I told myself I'd work until we hit $1 million in net worth. We hit that. I then told myself I'd work until we had $1 million in LIQUID net worth. We're working toward that, and if the market is kind we'll likely hit that in about a year's time. I can already hear myself making my next argument, though--after we hit the LNW goal, it'll be, "well, I should work until the house is paid off." Knowing me, I'll come up with some OTHER goal after that one is accomplished.
All of these are good things to do, good goals to have--but deep down, I think they are just smoke screens for the real reason I'm still working: guilt, which itself is just another smoke screen for the REAL real reason.
It's fear. Abject fear. Fear of being penniless, homeless, resource-less. Irrational? Probably. But convince the scared child inside me that it's irrational. Go ahead. I'll wait. ;-)
I guess what I'd say to you in your situation, based on my own similar-but-not-identical experience, is this: beyond wholesome prudential planning for post-career cash flow, your goal of having a paid off house before you pull the trigger is an arbitrary one, established by you as a couple and as such alterable by you as a couple. Take a look at the numbers, and take a look at your heart--model the reality of your both quitting financially, mentally, emotionally, and see what it has to tell you. You may be able to construct a reality that you can both be comfortable with bringing to life.
(Can you tell I'm talking to myself here as much as I'm talking to you? Thanks for the opportunity to reflect!)