I'm using the stock pads and they're still fine after about 3 years of almost daily use. Of course this can change depending on how much you sweat, how oily your skin is, makeup or other skin products, etc.

On the X2HR specifically (not sure about the original X2), the pads are trivial to replace on these as you just snap the plastic ring that the pads come with into the armature. See e.g., the picture on these replacement pads, on the X2HR you don't even have to rely on the adhesive, there are pins the headphone that just snap into the holes of the pad plastic ring that you can see in one of the pictures.

One thing I'll mention though is that there doesn't seem to be official pad replacements being sold by Philips, and the Dekoni pads for it are not that cheap (relative to the cost of the headphones). Not too much of an issue for me at least if they're as durable as the stock pads have been so far.

You don't need dac/amp for these, they're easy to drive. Even an Apple dongle which I use with my phone is more than enough to power them to louder volume than I'd be comfortable with.