How often did the Philistines fight against the Israelites?
1 Samuel 18:30 (ESV)
30Then the commanders of the Philistines came out to battle, and as often as they came out David had more success than all the servants of Saul, so that his name was highly esteemed.
It appears as if there were numerous small-scale skirmishes between the Philistines and the Israelites. These skirmishes were probably focused on various towns and cities; raids carried out to plunder and destroy (see 1 Samuel 23:1–5).
30 Then the commanders of the Philistines came out to battle, and as often as they came out David had more success than all the servants of Saul, so that his name was highly esteemed.