In reply to Flying Monkey: It's possible. Big but though, it's a massive day. We guide groups around in 24 hrs, most fail because of weather or lack of specific fitness.
You need to be hill fit, use to walking for 12 hrs plus but up and down big hills, not just up, along a ridge, down. We've taken 2 groups around recently, both contained pretty fit lads and both took 20-21 hrs. A long day.
Every group we've taken on it have said they underestimated it. This has been semi pro footballers, Mt Blanc summitters, triathletes, runners, rugby players, all fit guys, but not many specifically hill fit.
Also be able to navigate, you don't want to waste time. Having car support helps a lot, having friends/family to encourage/feed etc at the road stops has been crucial for the groups we've got around.
Also be fine to handle Crib Goch, it's easy technically but you want good weather and a good head for heights.
Good challenge, but it's a big step up from most other challenges. A good intermediate challenge is the Welsh 1000m peaks. The 4 peaks, over 1000m high in Wales. Start at Aber, walk up Carnedd L and D, over the back of the Glyders to Pen Y Pass then up the 2 snowdon peaks. Takes 10-15 hrs for most.