I think you might want to track these numbers instead:

• Number of properties. $lb is list, so the larger the number of elements in a list the longer the time to get to the last element. Also larger larger lists exhaust the global buffer faster, so they might be less optimal. 
• Method size in sloc. Ideally, your class shouldn't have methods spanning hundreds (thousands) of lines.

I wouldn't worry about total class length, but rather the number of individual elements and method sizes.

There's also class limits docs, but if you hit them, you probably have an issue already.