As long as you remember to keep '127.0.0.1 RM696 localhost' in the hosts file and make sure that the line endings are in normal unix format there should be no problems. Running custom hosts file for months now, and it is adequate measure against ads.

You also don't have to update the contents all the time, maybe once a year is enough.

Remember to
grep -v 127.0.0.1 /etc/hosts |less
to check that there are no malicious proxy addresses amongst the blocked ones. Speaking of which I'm not sure this is enough if someone puts a malicious line like this in the hosts file:
xxx.xxx.xxx.xxx mobile.bank.com 127.0.0.1

So grepping for your bank's name and your email address provider is adviced too.