Can a strong committed long-term relationship exist without any sparks whatsoever?

Only if both people have come to an agreement and are comfortable with what their relationship is: a) a deep, valued friendship towards each other, or b) an arrangement for financial or family purposes.

Answer

Sadly, most relationships mature into a casual relationship. The 'honeymoon period' which is the period of 'sparks' is said to last a maximum of only 2 years. After that you can have a perfectly amenable long term relationship, but can't rely on heavy emotions to keep you together. But there should be some occasions for sparks. Partners should make time for each other. It is, in fact, their responsibility to each other to make sure that needs are met.

Answer

Yes, it can, but it will probably be morelike a close friendship than a love-relationship.