PM question on length of time for Mash

Hi all, quick question:

For a partial mash, what is too long and what would be the result of mashing too long? Let me clarify why I ask:

I brewed an ESB this weekend and used the following ingredients. 3 pounds Maris Otter, 2 pounds 2-row US, 1 pound Crystal/40L and 3.2 pounds of Xtra-Light DME.

I mashed the 6 pounds of grain at 153 degrees. Problem was that I got distracted and did not sparge until after a full 90 minutes of mashing. Target OG was right on at 1.051 prior to closing up the primary. I used 1.5 q/lb of water too for the mash (9 total).

Does the longer mash time cause problems?

Thanks!

i usually mash for 90 mins and consistently hit my targets. i cant say that i know of any real issues with mashing for too long. once conversion is complete, its complete.

I've never heard of any problems with mashing too long either. With that said I wouldn't try mashing for days at a time but 90 minutes is nothing to be worried about.