I know you asked for scripture, SueAnn, but the more I looked through scripture, the more convinced that there is no "rule" about the number of times one should pray for any purpose. There are times I pray once and times I pray for years. For example, every time I see my one son, I gently remind the Lord that he's not saved.

I've been reminding him for about 10 years now. I don't think He minds. It's because I'm human that I feel the need, not because I lack faith and God knows that. Once in awhile, I even identify myself in prayer by telling him the street I live on.... it's just my way of saying I feel like He's forgotten me. I don't think He minds.
There are all types of prayer; i.e. petition, thanksgiving, burdens for souls, repentance, etc. Nearly every night, I thank the Lord that I have a roof over my head and a bed to sleep in. Prayer is communicating with the Lord and I think He loves to hear from us.....
When my sons call me on the phone, I don't pick apart everything they say or the way the say it. And thank God, when I repeat the same story over and over because I've forgotten I told them, they don't correct me. They are just happy to hear from me.
God's an awesome Father who's happy to hear from us imho.