These issues are very hard to diagnose. What is happening is that the cylinder is filled with oil when the lift is up. When sitting, the oil is leaking. Need to find out where the leak is, and therein lies the problem. The cylinder is internal, under the top cover kind of inside the transmission. Because it's inside, you cannot see where it's leaking from. Could be from the valve, the drop speed control or the cylinder itself...or between the valve and the cylinder (o-rings), the seals on the piston, the seals on the drop speed control. So there are a lot of places oil can leak past.
The dealer is helping you, or trying to anyway. I've not personally heard of these having big leakage problems, so that points to Kubota's RSR having to perform "exploratory surgery"...meaning, they're going to have to take it apart, replace stuff, reassemble and try it. On a B-20 series, you're looking at 4-7 hours each time and that's working pretty fast.
So you want a new one. That's a tough call, and Kubota's customer service is the only way you'll get anything done in that department. The B2620 is no longer made, so you'd have to get into a B2601 which replaces the 2620. It's also more expensive, so if Kubota were to give you a new one, you would be out the price difference at a minimum. The 2620 and 2320 were proven tractors, and honestly, knowing what I know of the 2601 and 2301, Keep what you have and get it fixed. Just my thoughts on that issue, for what it's worth. Keep in mind that when it comes to "major units" (tractors, RTV's, 4 wheelers, the big stuff), dealer's aren't like Wal-Mart in that if you don't like what you have, don't expect a refund or no hassle exchange. If that's what you want, you're going to have to work for it.
Also keep in mind that Kubota has a drop rate specification..I dont know what it is, but on loaders, 2" per hour is the accepted rate. More, and there's a leak. Less and they aren't going to spend much time trying to fix it. I'm sure the 3 point also has a specification, I just don't know what the actual rate is, whether it be 6" per hour or .5" per hour.