lifer

— They know what a clever lad he is; he'll be a lifer. They'll make the Artful nothing less than a lifer.

— "[…]The Top's not a lifer; he's a career Marine. Lifers are a breed. A lifer is anybody who abuses authority he doesn't deserve to have. There are plenty of civilian lifers."

— It is difficult to classify them precisely, but, in roughly ascending order of productivity, we now recognise the purely chance observer, the locality regulars (now recognising that ‘time in’ eventually equals ‘rarity out’), the ringers (particularly when working in groups), the occasional tally-hunter (most of us, if we are honest), the full-time observatory workers (exhibiting the highest standards of discipline) and the growing group of full-blooded rarity collectors (self-styled ‘twitchers’, covering individually up to 30,000 miles in their annual pursuit of ‘lifers’).