You said in that 18 hour window your rig was on we were mining LTC for almost half the time? It couldn't have had to many switches if that was the case. I know with my setup I have it set to change coins an check profitability every 5 mins. Even though I am switching almost every 5 mins I get a much better payout with the same hash power as on multipool. So the idea of switching coins often shouldn't affect profitability depending on the payout scheme of the pool. That said the more multipool switches the more stales/rejects I get. That's not the case when I use separate pools rather than one that port forwards to a different pool/port.
No I said "we" were mining it, i.e. the multiport. The point was it's a slow coin so there wouldn't have been a lot of new blocks to cause stales like if we were on WDC or something. However, the multiport switched coins about the normal amount of times.