the main resource to consider is Broker memory

depending on available Broker memory, a reasonable range for total # of open statements on a Broker would be totaling 50–300 across all connections

the defaults get you a max of 100 (the default max connections is 25, and default max statements per connection is 4)

you could also check to make sure your JDBC clients are closing statements properly

if some JDBC client leaks statements then it can use an "unreasonable" amount