After a particularly nasty cockroach invasion ( well, I don't suppose there could be a nice one
) a few years ago I had my house sprayed. I now have it sprayed every year, usually in late April. Critter problems have disappeared.
As a result of this success, half a dozen house owners on my complex, and a fair number of non resident friends have their properties sprayed at this time.
The result is cockroach free premises.
The only exceptions occur when the houses / apartments have been occupied for holidays etc and then closed up until later in the season,then used again. Sometimes there is a minor but nevertheless irritating ingress of the dreaded cockroaches. It seems the little blighters know peoples holiday plans! Indeed the houses which are permanently occupied remain clear of infestation all the year round..
Oh, and by the way, the gentleman who does the spraying ( head barman and occasional belly dancer at a well known Calis Bar / Restaurant ) only charges 25 TL, which for my place of ten rooms plus loft spaces, stairs and landings is I reckon a real bargain.