Slush's total hashrate says we should solve a block ever 4 hours and 41 minutes, given a large enough time frame and assuming constant difficulty. This has proven practically true until recently.
The average time to solve a block in the last four days (15th through the 18th) was 4 hours and 54 minutes. That's exactly in the range I would expect, despite our recent 25 hour sojourn. Let's not forget that we solved 8 blocks on the 15th. That is a good deal above average. Overtime, these things even out. You might be tempted to pool hop, in hopes to avoid the lows and cash in on the highs, but that is really just gambling and might seriously backfire, like it did to one person who posted on the previous page.
I prefer to stay in one spot where my returns are predictable over the coming months.