I know two couples and one (who has just sold) who are/were desperate to get out of the B&B business.
The hours are much longer than some people may think and even with room rates in the £100-£160 per night range you have to go some to make any real money at this unless you own the freehold of the property outright.
It can be a good business if you graft at it and are not financially encumbered and imo it is a younger persons game - depends how old you are when starting your retirement I guess.
We looked at a 10 bedroom B&B in Ambleside in 2008 (friends of ours) on the market at £880000 and whilst the annual numbers were not too bad the real money for the sellers was the increase in value of the freehold - they'd bought it for just over £400000 around 7 years prior. Most B&B prices have tumbled up here the last few years with many properties being very difficult to sell and being on the market 3/4/5 years etc. Not sure the 'good times' will be back for some time.
You also need to sell your soul, and a substantial amount of money, to the likes of booking.com to ensure that your occupancy rates are high.
Also, you need to budget to continually update the premises (expensive) as guest expectations are continually rising with many often expecting (not always getting which equals complaints) a boutique hotel with a permanently available member of staff on hand from a B&B.
Also, expect problems from some nationalities booking rooms for two and then trying to squeeze extra guests in on arrival.
Bit negative but if you take the leap I hope it goes well for you and please do have an exit plan that you can quickly enact if one or both of you get ill in old age. One of the friends mentioned above is in dire straits - her husband left her some time ago (affair with old girlfriend via FB) and she is 67 with several ailments that are making life very tough for her to operate (finding staff up here is a nightmare) and her premises have been on the market since early 2016.