Due for a downswing -- a put credit spread on SDS

I think we are overdue for a couple of down days.   Sold 20 Jan SDS 35 puts at 1.17 and bought 20 Jan SDS 34 puts at .62, for a net credit of .55.  SDS was at around 34.5 at the time.   I tried initially at .56, which split the spread, but it didn't fill after around 15 minutes, so I bumped the credit down a penny.  Then it filled within a couple of minutes.