Can I file a personal tax filing extension 2 or more years in a row without consequences i.e. No different to doing it once?

There are no adverse consequences to filing extensions for several consecutive years.  If you need more time to finish your 2016 taxes, don't hesitate to file for an extension.  Otherwise, the IRS will likely impose a penalty on you for filing late.

What about Self-Employed taxes? Thx very much for quick answer.

Makes no difference.  But remember, an extension to file is not an extension to pay.  If you owe taxes you should at least make a partial payment with your extension.

Thx very much again