Spousal Visa

I arrived in Zimbabwe in 2013. Since then I applied two times for visa extensions which where granted (for US$300.00 per extension). Last year I applied for permanent residency based on me being here for +5 years. The visa was denied but I got another two year extension. No reason given. I did pay however US$500 this time as I applied for permanent residency... So I asked for a US$200 refund which I of course didn't get.
The immigration officers here in Bulawayo hinted that the fact that me and my wife don't have children is showing lack of commitment. I'm 55. I think it's BS.
Does anyone out there have similar experiences?
Should I just continue applying for visa extensions and save myself US$200 every 2 years?