As I understand it, your 180 days started when you purchased your visa in April, you were then able to stay in Turkey at any time during the next 180 days, as long as the total didn't exceed 90 days in total. Your next visa therefore can then start at anytime once (but not before) the 180 days has expired. The process as explained then starts once again.
Re residency, we visit our villa 4/5 times a year and visit typically for 16-20 weeks, so the decision to get a residency permit was made somewhat easier for us. The rules for residency are due to change next April, and at this point in time, no one knows wether the new rules will be more cost effective, or indeed more or less difficult to obtain. But our visas expire in January next year, and we have decided to take out the present maximum available (5 year residency) at that time, as we feel the cost and process presently are neither expensive nor onerous.
