Maximum No of Sender File Adapters in one adapter engine

Hi,

what is the maximum no of sender file adapters we can use with a single adapter engine(having only central adapter engine) ? we are using around 15 sender (inbound) file adapter communication channels with an average polling interval of 10 mins - 30 mins, because of this the system became very slow and j2ee server process is taking more than 50% of CPU time.

Has anybody deployed more than 15 sender (inbound) file adapter comm channels in the impletation and went live successfully ? Please share your experiences regarding this.

Thanks

Pavan.