The thing to keep in mind if you are adding to the Liquidity Pool for the main purposes of gaining SPS is that your DEC in the pool is not constant. If the DEC price increases you will end up with less DEC in the pool (and more BUSD), so your airdrop power will drop - you would have been better off holding the DEC. If the DEC price decreases you will end up with more DEC, your airdrop power will increase, and you will be better off in the LP, rather than holding the DEC. So putting your DEC in the LP is a bit of a hedge - if DEC goes up you have less airdrop power, but probably all your other assets will increase along with the DEC pool (and vice versa).

I learned this the hard way - I had a bunch of DEC in the pool when DEC was at its peg, and by the time the price run-up occurred I had roughly 1/3rd as many DEC as before (and so 1/3rd as much airdrop power). The value of my holdings in USD had roughly tripled. I would have been better off holding DEC (same airdrop power, value 7x), but that is easy to say in retrospect. This is the "impermanent loss" issue.

That doesn't take into the account the CUB I earned through the LP, which is a nice boost.