Define a local table at the top of your addon and use keys instead of separate variables.
For example:
Lua Code:
-- instead of this
local a, b, c, d, e = 1, 2, 3, 4, 5
-- use this
local vars = {}
vars.a, vars.b, vars.c, vars.d, vars.e = 1, 2, 3, 4, 5
You can even use the provided addon table in the second vararg return that's handed to each of your addon's files.
Lua Code:
local addonName, addonTable = ... -- the very first line of your addon file
This addon table is shared across all your Lua files under a single .toc file.
I honestly wasn't aware of a local variable cap, but I've had tables with thousands of entries in them.