As from personal experience and usage, I would encourage you to change those variables into constants. This is the usual scenario about why:
If you keep them declared as variables and try to use them with functions within your site, you will find that though you include the variables with files that have the functions you want to use, the functions cannot see them as they do not live in the same scopes. So you end up going to each function you need variables for and declare them using GLOBAL $blah1, blah2, ... so on and so forth. Eventually, any time you need a new variable, you must remember to tell the function "Oh yeah, this is a global variable that you can't see, just trust me and use it."
However, if you declare those variables as constants, there is no need to do the GLOBAL thing in any functions.
Just for some edification, including files with constants is a good way of working with things, 😉.