Tier1 General - earnings requirement for 5 years

Hi Friends
I have been reading some posts on this forum regarding Tier1 general – ILR route. I am due to send my ILR application on 5 year Tier 1 General- ILR route in August this year. (10 year route applicable in Jan next year)
I would like you to suggest the best on my circumstances. I have been earning above 35k requirement in years prior to my initial HSMP application, Tier 1 extension application and prior to this coming ILR. But due to my circumstances, my earnings were much below the mark and did not met 35k limit in all previous 5 years. My understanding is that as long as earning are above 35k in the last 12 months prior to the application, one can earn points for the earnings. Is there any requirement to have the earnings over 35k in all previous 5 years for my ILR route?