We all have different levels of libido - both men and women with high libido's may need to have sex more often just in order not be thinking about all the time - it sort of starts crowding out other thoughts.
Men and women tend to have different priorities, reflecting evolutionary developments - men have generally evolved to spread as much semen as possible - i.E., men who have sex a lot tend to have more offspring that they passed this trait onto, while women more typically seek resources to increase the probability of raising reproductively successful offspring - i.E., quality over quantity.
I wouldn't feel too bad about helping him out if the relationship is important to you, sacrifices have to be made in any relationship, unless it's actually causing you physical discomfort or damage - try fantasizing, or porn to see if you can gear your libido up, there are worse problems in life than having sex too often.
At the same time, communication is probobly the single most important factor in a successful relationship, I think frequency of intercourse would have to take second place there, so if you are fearing for the stability of your relationship, it's the communication factor i'd be looking at.
My ex and i, for example, were well matched libido wise: we both liked it at least once a day, although she often wanted at times inconvenient to me, when I was in the middle of something else, but we didn't communicate well (or at all) in other areas, which eventually spilled over into the sexual department, and that (communication, or lack thereof, not sex, although it was a factor) is what eventually tanked the relationship.