Is it commonly accepted to postpone an Email for long time?

I have so many Email accounts that I use for various reasons. The problem is that I will not check all these secondary accounts every so often (I guess I’m quite lazy, or forgetful), except for a couple of my prime accounts.

Some people I know from various sites have sent me Emails to know me, or to simply chat with me but I postponed their Emails for quite a long time (a few weeks, some even for months), and when I finally send a reply to apologize and explain my situation they never send back. I’m curious if they’re mad at me, or it’s simply acceptable, or has been the habit for the majority of people to have so many Email accounts and postponed their secondary Emails? Will you please enlighten me?