Often this kind of expression (xx头) is frequently seen in literature works or in a vulgar tone, in my opinion, there is a simple way to find out it's meaning in the context:
- Modify 年头 with a definite ordinal number, e.g. 第1个年头,第2个年头,第10个,第n个年头,in such case, 年头 simply means year, the first year, the second year, etc.
- Modify 年头 with other determiners or quantifiers, such as:这(this)年头,那(that)年头,那些(those)年头,有一些(there have been some)年头了,for these cases it means an indefinite period of time, or years.
so the translations would be:
这年头:these years(pay attention that it's not 'this years' because it's talking about an indefinite period of time instead of a specific year, so you have to make it plural/unspecific in English.
那年头:those years
这些年头:equals to 这年头,both talk about unspecific period.
那些年头:equals to 那年头
有些年头了,有好些年头了:there have been some years that ...
Also you may encounter another similar expression "这日头,这些日头,那日头,那些日头,有些日头了", what you need to do is to replace "year" with "day":
这/那些日头:these/those days
我学中文有些日头了:I have been learning Chinese for many days.
As I know, besides these two usage, there isn't 这月头、这时头,这分头,这秒头,etc.