When i need extension for next 30 months. So i need only 6 months pay slip and tax not for 30 months.is it. Thx

I got married in uk in 2013.my wife is british born n citizen. In june 2013 i got spouse visa for 30 months till dec 2015. Me n my wife was doing part time jobs.n show share income 18600. Now m working full time .but my wife left the job. Now m worried when i will apply for extension for next 30 ...