You sound like you're treating your 1st to 2nd shift like you treat your starting from a stand-still.
1st to 2nd is clutch in, shift, clutch out, back on gas. No need to feather the clutch and balance the gas while you're already driving.
Holding the clutch pedal down while not moving won't wear the clutch, but it can wear the throw-out bearing. Shifts should be a fluid movement. When I shift, I jab in the clutch pedal then shift and release the pedal all in one movement. I don't hold the pedal down between shifts, it's down to the floor then back up again in maybe a second.
Unless you're constantly dragging the pedal or just being dumb, a clutch should last a good while, I'm still on the stock clutch at 130k miles and I have zero slippage as tested by driving 35mph in 5th, gas flat to the floor. Doing this will point out any deficiencies in the clutch as this puts a really heavy load on the drive-train.