The hobby has changed quite a lot between the 135ths and now.
For starters, the hobby is half the size it was, even during the 140ths. Infantry battalions that could field 400 men are now struggling to get 200. However, artillery does not disappear. In the struggle to keep pieces on the field, I've noticed that some units have taken to dressing up more and more women-just to fill all the positions.
In the East, there are eight Federal battalions, roughly two brigades of shot-up troops. This accounts for less than 1,500 troops on our best day. If a division's actions are being portrayed this leaves room for, say, two batteries of guns? We almost always push the limit to well beyond that. Try to write a historical scenario for that!
Then are are the two events. I think that these are good things. They give reenactors more choice. But it always seems to come down to the fact that some have greater demands from themselves and the events they attend. This reduces the number at each event.
Events also tend to inflate their numbers of "participants." Last year, the 150th Bull Run had approximately 8,000 reenactors. 2,000 of these were civilians. Another 500 or more were Artillery and Cavalry. That leaves 6,000 infantry. Maybe 3,000 Infantry per side. If, for example, Maryland My Maryland reaches its limit of 4,000 participants, it doesn't leave much for the other. In short, the days of the 15,000 soldier events are over for a while. I'm OK with that.