I haven't tried this but I guess this holds true for all the Key words ..Printt, Forr, Nextt, or Prints, Fors, Nexts even Too as a variable ...I like Loopy .. but as xra7en has just pointed out, the variable maybe too close to the key word.
One thing to consider in variable names in a large program is search-ability. opens is okay to use as a variable name, but when you search for OPEN to find file operation statements, you need to match case or search for the exact word, otherwise you end up finding all the opens variables, too.
For files, I use f1$, f2$, etc. or myfile$
Also, I think ending a string variable with an "s" looks a bit weird when followed by the dollar sign... opens$. Others may feel differently, but as we all know, my opinion is the only one that counts... in my opinion.
Pete