First day back in the water

Ouch.  Long course meters is a rough re-entry into swimming.  I wasn't sure my arms were going to keep moving after 3,000 meters.  Long course.  My cardio was okay, but the lactic acid was really building in my shoulders.  Nonetheless, I'm going back tomorrow.  I'm about to "age-up" to the 30-34 age group.  Which could be good, those older women are slower, right?  I haven't thought about aging-up since I was 14 and it was with great dread then.