As above it really depends on the boat and the weather. The stretch from Ardnamurchan to Mallaig or Rum or one of the loch on the south coast of Skye is open to the SW, so can be subject to an ocean swell, but the rest of the trip is reasonably sheltered.
I've done it several times, you should be able to do it in a week at a fairly leisurely pace, given a reasonable forecast the skill level required isn't that high, but you need to be able to get the tidal gate at Kyle Rhea right and although the tides aren't that bad elsewhere, you can expect a knot or less at neaps and between 1 and 2 knots at springs, so it's worth going with the tide when you can.
Why not get hold of the pilot books and charts and do a tentative passage plan?
You'll know what you and your vessel are capable of in terms of speed and how long you are able/prepared to sail each day, much better than anyone on the forum.
Some of the distances round the north west headlands are reasonably big - and often very few other boats around. It can feel lonely if hit problems there (we had Loch Harport all to ourselves lsst week).
On the other hand we met three lady kayakists who had just done it
Skye is a marina-free zone. Some of the best anchorages are down the sea lochs so you could end up doing a fair number of detours which would add to your mileage. Probably best to do the west side in two or three larger hops.
If you see a tatty little blue and white Bradwell 18 when you do it, say hello. I'll probably be doing something similar, either late June ish or July. I'll only have had the experience gained from getting that far from Cumbria, (if I do).
Some of the best places to stop are not on Skye, for instance Canna is a much safer harbour than Scavaig or Loch Harport though if the weather allows it would be a shame not to get there, nothing more dramatic than waking up with the Black Cuillin towering over you. When you get round the top a diversion to Gairloch and Acarseid Mohr are more interesting and nicer harbours than Portree. We tend to circumnavigate Skye using the above harbours sometimes with only one stop on the big island, at Stein which has a couple of moorings and a really good pub. If you go to Canna now the puffins will just be getting ready to leave, practicing flying by diving off the stack and you will have the added thrill of being dive bombed by the bonxies on the hill behind. The Inner Sound is very sheltered but Kyle Rhea from Glenelg southward can be a nightmare if trying to get south in strong south westerlies, Mallaig is horribly exposed to the North, a few years ago we were trapped in a very full Kyleakin for over a week in early July. (the pontoons at Kyle are closed in strong weather so the only choice is a long raft in Kyleakin or move on)
thanks all for the advice. If I do summon up the courage to go it will be in June and I'll keep a look out for those of you who might be there also. Good luck
If you find yourself down Loch Greshornish, I'll maybe come and say hi. It's a bit of a detour from your circumnav but a good sheltered loch with decent holding. One of the better anchorages from a technical point of view, but not much in the way of facilities ashore I'm afraid.