I feel sorry for anyone that later ends up with the same number - there's a limit number, after all. Having had the pleasure of a landline number that was previously owned and advertised by a local company, and a mobile number that used to belong to a mechanic hundreds of miles away, I can see potential for some awkward calls here!
I used to have my old smart phone as my punting phone, with a PAYG sim in it, when it began to fail I got hold of the cheapest nokia I could find (as always got on well with these) and stuck the sim in there. Got a sim with the new phone as well, as the phone was far cheaper that way, and got the credit transferred across to my real number. Actually keep another sim for a different network as well, and as my phone is unlocked I can easily swap that on in if there's a signal problem at the important moment.
Works for me - the nokia is fairly small and light (far smaller than my old smartphone) and offers all I need to call/text, which is what is required when on the way to a wg. I think it can do email as well, but I've not bothered setting that up - I still have my main phone, and can email from that if I need to.