You've left out some important information: how much does your pack weigh without the chair for a 3-day trip? Are you comfortable carrying that weight for 30 miles over 3 days, or do you simply collapse at the end of the day?

If you're carrying 20 pounds for three days, and you hike easily with that weight, then heck yes, take it if you feel like it will make the trip more fun! If you're carrying 60 pounds and hiking easily (i.e., if your trail name is The Hulk), then you'll never notice 2 more pounds, so go ahead and take it.

However, if you're very sensitive to weight, like most of us on these forums, you'll probably want to leave it behind. Personally, I can tell the difference in how I feel when carrying 15 versus 20 versus 25 pounds, and I'll take lighter every time.

I have carried chair kits (though I don't very often, anymore.) The heaviest weighed 16 ounces; most weighed 6 or 8. They're the kind that use your sleeping pad to give it stiffness and comfort, not the use-as-chair-only kinds like, I assume, yours is. I particularly like the full-length versions, or the kind with an open front (see MSR Compack chair), so I can let the pad extend out under my legs, more like a lounge or recliner than a kitchen chair. (Note: I also carry a ground cloth, and the chair kit goes on the ground cloth, for that tiny bit of extra protection for the pad.)

I usually don't even carry a sit pad - it's usually pretty easy to find a soft spot (some grass, forest duff, etc.) to sit on, and a tree, log, or boulder to lean against. As mentioned earlier, I've also used my pack, propped up by my trekking poles, as a back support. The only time I consider a sit pad nowadays is winter, when the ground is c-c-c-old.