established remote vpn link drops and reconnects

I have this current setup:

Site A
Office location that is behind an RB750 providing firewall/nat/pptp server.

Site B
I have remote office that is behind an RB750 providing firewall/nat/pptp server/pptp client. This site has a webcam and another computer which controls some local machinery.

The two sites are connected via the internet on two different ISP’s. Both sites have a static IP.

Site B connects to Site A via PPTP and maintains connection for a given amount of time something like 2-3hrs before dropping the connection. At this point Site B re-establishes the VPN tunnel with Site A and is good for another few hours before the same thing happens. This happens continually over the course of the day and night. Should I be worried about this dropping? Shouldn’t a PPTP link between two Mikrotik devices be pretty solid for a long time? Maybe I am worried about nothing? Some times no one is active on the PPTP link so maybe this behavior is normal?

Thanks for any help,
Aren

I need to know the same thing above, but my drops has shorter period. Thanks in advance.

funny thing is that after i posted this, the connection has been online for >19hrs now!?!

Aren