Files buildup in that folder based on whether or not the SEPM/Database can process the requests fast enough. More details like how many clients, system resources, database type, heartbeat (push/pull/time), and other things like replication, any additional features (Learned applications, Network Application Monitoring, firewall logg) being installed will have an impact on how fast your heartbeat can be.
Are the files .dat, .err, .tmp? When were they created?
I would start by putting your heartbeat in pull (if it isn't already) and then increasing the heartbeat (maybe start by increasing it by 30 minutes). Without knowing more information about your environment any further suggestions are hard to make.