If you don't run multiple mags on full auto or go through 8 mags in a few minutes I'm pretty sure baffle strikes are very rare.  

Most baffle strikes are caused by poorly threaded barrels, defective or not properly mounted quick attach systems or abusive fire schedules.

If you mount your surefire can on a 12.5" barrel rather than a 10.5" barrel I'm sure you probably reduce likelyhood of issues by 20-30%.

The exposed lead base on a 9mm is larger, the suppressors normally operate cooler, and the pressures are lower creating more optimal characteristics for leading.  

5.56mm suppressors shouldn't foul as badly or nearly as quickly, simply because to some extent temperature, pressure, and particles are going to blast some fouling away.  

I think what ends up happening is that copper fouling is more likely to build up in 5.56 suppressors because it has a higher melting point and isn't as soft as lead.  Obviously copper fouling is greatest when the rate of fire is most excessive and barrel temperature is elevated.

There are a lot of people with suppressors that have run 6000+ rounds and are working well.  One Gemtech customer had around 100,000 rounds on a M4-96D at which point some significant buildup had occurred.  It's a horse apiece at that point- you either build a can that comes apart and has potential for mechanical issues that can make it in-operable, or you weld one and fouling eventually claims it.  Suppressors don't last forever but they do last a long time.

I think it's very rare for a person to fire more than 7000 rounds and there is little reason to be worried about suppressor fouling.  

People that post about fouling and cause people not to buy suppressors aren't doing anyone a favor.

5.56 suppressors that come apart for cleaning aren't a good idea in my opinion, and worrying about suppressor fouling to the extent that one doesn't buy a suppressor is like worrying about car trouble and spending your whole life riding a bicycle to work.