Obviously a longer cock will be easier, but your cock doesn't have to be huge. Mine (measured along the top) is 6-3/4" and I can get the head in my mouth to suck.

The key is, don't assume you can't do it just because it is like 6" from your mouth when you start. I find the best position is on a bed, flip my hips over my head with my feet on the headboard to push against. I start stroking and just let my body get used to it. When I first start it might be 4-6" from my mouth. As the minutes pass I push with my legs against the headboard to try to push my cock closer to my mouth. My back starts to relax as time passes and eventually can touch my tongue to the tip. Many times I can't get my lips to it until 2 seconds before I cum. For some reason, at that moment my body seems to give way and I can move it that last inch or 2 to get the tip in my mouth to shoot my load straight in

downside: I find that when I'm done, and try to straighten back out, that my back and neck are REALLY sore. But usually goes away in 30 minutes to 5 hours. Maybe if I did it more often I'd not hurt as much and could get the tip in immediately. But I only do it maybe twice a year.

Pleasureable?: I love it. If my back didn't hurt from it afterwards I'd do it a hell of a lot more often.

I hope that helps