I know how you feel.
One of our neighbors has "warned" us they have to leave due to ill health.
They are not that physically close as the houses have a fair bit of space.
But these neighbors are just about perfect - anyone coming in will not be as good.
I am allowed to say that now before they come!
IE -they only use one car - the norm is three or more.
Most drives take five and the extra coming & going with do nothing to improve our quiet nights!
My dear old neighbour Bob died last year, and after several months we had a young couple moved in. We were a bit sceptical as there were a lot of their young friends at the beginning but it seems they were only helping with the move.
They have proven to be good neighbours and recently gave my wife assistance with bins etc. while I was in hospital.
But I have always treated mine as I would like to be treated by them, and we all get on fine. No problems at all. Except for one old "Biddy" a few doors away who will not even say hello to anybody. Her neighbours tell me she is the one from hell.
Not sure if it still applies elsewhere in the country. But it was once a great social idea viewed by national or local governments, that placing a 'problem family' among a host of 'good families' was the way forward.
Glad that idea didn't really take on, or did it?.
Fortunately, all our neighbours are in the main long term, and while not being to nosey, are always there for help, when the occasions arise. Perhaps just the way it should be?.