My objection is precisely the opposite of what some have said here.

You are affecting the outside world, but only negatively - using resources that could be put to more important things than one person blissing out, without creating anything for anyone else. I therefore see wireheading just you as an unethical choice on your part.

I am not sure if I have an objection to "wirehead everyone sustainably forever", if that were ever practical.

Edited to clarify very slighty:

I do have some revulsion at the thought but I have no idea what it would be grounded in, if anything.