Wendy, I have 2 Wilderness Systems Tsunami kayaks. In my opinion, I would never get one for trip kayaking. I have done 3 day trips in mine in fairly sheltered areas. They don't handle very well in the rougher stuff. They weather cock badly (a rudder will help solve that), they are not very fast, and they don't have very good secondary stability. But they do have a fair amount of space and a good size cockpit. I guess it all depends on what you want.
I also have a Wilderness Systems Tempest 170 and I just ordered a Valley Nordkapp. The Nordkapp is an 18 footer and the Tempest is a 17 footer. Both these boats are great sea kayaks and can easily handle a 2 week trip. They both have very good secondary stability, lots of space for gear, track great, fast, handle great in waves, both have skegs, and they are good looking boats. The Nordkapp has probably the best hatch covers out there. And I like the fact that it has plastic welded bulkheads (I have had some trouble with leaky foam bulkheads). I am getting the Nordkapp to do exactly what you want, 10 day trips. I don't know how good your paddling skills are but generally new people to the sport may find the Nordkapp a bit tippy.
These are my opinions only.
When I bought my Tsunami's, I didn't really know what I wanted. I outgrew the Tsunami my first year paddling. I would not buy one today knowing what I want to do. I keep them now for family and friends to use.
What ever you do, test the boats out. It will certainly help you choose the best boat for you.
Good luck and safe paddling,
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