Do i have to create a certain nonclustered index every now and then?

Do i have to create a certain nonclustered index every now and then?

I have a database table that has more than 50 Million record and to
improve searching i had to create a non clustered indexes, and once i
create one it takes 5 ~ 10 minutes to be created so i guess in the
background it sorts the data according to the index.
So for example before adding index to my table searching was awful and
takes long time and when i added the non clustered index, searching was
fast.
But that was only when i had 50 million records.
The question is, what if i defined the index at the very beginning when
creating the table before adding any data to the table? Would it give the
same search performance i am getting right now? or do i have to delete and
recreate the index every now and then to sort the data regularly?
I am sorry if my question seemed stupid, i just started learning about
indexes and it is a confusing topic for me.