Can I get a resident's parking permit for a car I park at my house for only a couple weeks a year?

I am a named driver on my sister's car insurance. She is the registered owner and policy holder and lives a couple hours away. She travels abroad for work quite a bit and is always happy for me to make use/keep her car at my house whenever she is away. I live in London where there is controlled parking zone on my street and want to keep parking costs down for the total of maybe 12 weeks a year or so I would keep the vehicle parked at my house. There is not controlled parking where she lives so it's not like the car would have two resident parking permit stickers on the windscreen. thoughts? Is this simple enough or would I get in trouble for this?