I think your mum has the right idea - enjoy the RE0s for a little while. Whenever I get a new hobby I get excited and buy lots of stuff without taking the time to enjoy what I have.
I've done something similar to you, recently bought and am enjoying two very nice IEMs and I also have the urge to upgrade to customs, however I think I'll wait a year or so and just enjoy what I've bought. My M6s are already gathering dust and they don't deserve it - they're awesome earphones.
In a year or so I'll be making the leap I think, in the meantime I'll be watching the forums so I can make a good decision when I do.
I know it doesn't help when you want new stuff
now, but it's ultimately more rewarding. You feel like you savoured your purchases and chose wisely when you upgraded, rather than bought heaps of stuff fast and hardly used most of it. I know because I do that a lot and it's very depressing at times.
All you other guys, stop whipping him into a consumer lust to validate your own high-priced gear addictions!
We need a rehab group in here or something..
From a more practical perspective, if you're as young as you seem to be, your ears might still be changing shape, which means your custom earphones will only fit for a little while. Of course I'm no expert and I don't know how old you are, so that may or not be valid.
Anyway, think about it, maybe use the time your mum has bought you to do some more research, or have a look at selling some kit to get a ER4P. Good luck..