Funny thing happened. I have a dedicated Slim Burn wallet on a computer I use only for this wallet (i.e. my staking Slim wallet does not reside on this computer).  Anyway, regular and healthy sized payouts of coins had been coming in thanks to burning.

After a couple weeks the staking started up (I suppose because my wallet was unlocked).  Staking rewards suddenly started appearing.

Exactly coinciding with the onset of staking rewards, 1) my computer slowed way down and 2) the burn payouts reduced to a trickle and became smaller in size. Though I was now getting small stake returns, this didn't compensate for the huge reduction in burn payouts.  

I'm assuming I shouldn't have left the wallet unlocked on my dedicated "burning wallet/computer" because staking takes too much processor power, even for small amounts.

What I learned is not to mix burning and staking, and therefore, to always burn with the wallet locked.  

The thing I can't explain is why the onset of staking rewards would reduce burn rewards.  Although the computer was slow, it was working enough to support several other non-Slimcoin wallets that continued to get staking rewards, and I understand burning isn't processor intensive.  So I'm a bit perplexed why my burn rewards got reduced by 90%.