Chain stretches more on the ratio im using for round here at 32.16.seems to me every couple of rides stretches far too much.
If chain snaps do you carry a spare bit of chain and 8spd powerlink?

Nope use a half link chain, reattach back together and slide in drop out to get correct tension

If your new chains are wearing out quick, it sounds like worn sprockets causing it.

or your wheel/tensioners moving …..

Sounds to me like your chainline might be away to hell.

A singlespeed specific chain like a KMC 610HX might help, although even 8sp chains don't stretch that badly.

And yup, a spare bit of chain is a good idea.

I don't mean to sound patronising, but are you sure your wheel isn't moving? Every ride or two seems impossible (or you have thighs like Chris Hoy)…

the cure

http://www.evanscycles.com/products/shadow-conspiracy/interlock-v2-chain-ec011381?utm_source=froogle&utm_medium=froogle&utm_campaign=froogle

don't use a chain tool on it, you will break the tool

do you drive a sherman tank to the nursary to pick up your wain ?

it's not unusual for a new chain to 'grow' quite rapidly early on, but it should settle down, unless you're just using 5hit chain.

The shadow chains stretch really badly.I ran them on my 20" for a while with simple slammers-chain tensioner that cannot slip,cos they physically fill the gap- and they stetch quite a lot from new before calming down.

no, I ride SS up hills and I weigh more than the average rider 😉

the only chain have have not ditched due to stretching

I had a Shadow chain that grew so much that I took enough links out to make another chain. 😉