After a dental check, my dentist suggested options of crowns and composite fillings. the crowns are much more expensive. do they have superior lasting?

Depends: It really depends on how much tooth structure remains after the decay is removed. If you are unsure it may be worth getting a second opinion.

Hard to say: Each tooth is a bit different, as is each patient. The problem with really large restorations is that they don't last very long. Crowns are not as conservative as fillings, and yes they cost more, but last longer in most cases. Since this appears to be a major investment for you, you can seek a second opinion if you are not sure.

Fillings vs crowns: While i can't know whether or not you need crowns, when necessary, they are generally a better option, protect the tooth more, and hold up longer. While the initial cost is more, it may actually save you money over the long run. If you trust your dentist, go by his\her recommendations. If you don't, find one whom you do. If unsure, get a second opinion.

Both same avg life.: Crowns and composite fillings have statistically the same "life span" however that isn't apples to apples comparison. A small composite filling often easily outlasts a crown (if cosmetics are it an issue). On the other hand due to initial physical shrinkage of the composites (the larger the volume the more of an opening for decay) and other issues large composites fail much quicker then a crowns.