Publishing my research after 4 years
Any novel work can be published regardless of what time it was first produced provided the following conditions are met.


The method/concept/matter itself was not published before by anyone. 
Inclusion of a survey of recent literature addressing the present significance of your work. 


The second point also includes a third: your work should be still of scope and interest at the present time. 

If the above factors are considered, it is (technically) never too late to publish. There are papers that are published that span decades of research. 

It also depends on the field/domain. For instance, when it comes to computer science, the sooner the better. This is because in fields where the current trend is volatile, you can never tell when your work will become obsolete or already published.