dumb vpn routing question

i have 2 sites i am connecting

one is 10.1.x
one is 10.2.x

when the tunnels are up and created everything is fine.

i have static routes built on both sides using the ppp tunnel as the gateway

my issues is if the tunnel drops or a router needs a reboot, those static routes go invalid as gateway is unknown since the interface drops (pptp-XXX) etc.

how do i configure the routing to come back once the tunnel reestablishes itself?

nothing?