Making time for people is really hard when you are busy. But you just have to force yourself. If its someone you are going to marry then they should be more important to you than anything else and that includes your job. Trust me. If your job is more important than your wife you will live your entire life and never ever be happy no matter how high you climb on the corporate ladder. The reason for this is that human beings' brains are wired to get most of their happy feelings from social interaction and only a little bit from self actualization. This is a big reason why more middle classy types are typically happier than people who want to be superpowerful.
Also, you should never be in an LDR for longer than a couple months at the most. Someone needs to move closer to the other one or the relationship needs to end. Trust me, you will be happier for it. Personally, I avoid LDRs like the plague. Just this year I've had to end two relationships with girls I REAALLLY liked because it was going to have to go LDR. Instead Im here at my college trying to find a girl who lives close to me. I'm doing this mostly for my emotional needs. LDR's create more pain than the joy they give you and if you dont love each other enough to make enough compromises that you are closer to each other locationally than you really dont love each other as much as you think you do.
Theres also the fact that almost 100% of the time that an LDR gets prolonged past a couple of months that one or both parties will start cheating. I know people who have been married faithfully for years, but as soon as the guy starts having to travel a lot for business. Its rarely very long before the cheating starts.
And some people think cheating is fine. In my opinion, if you are going to cheat, save yourself the hassle and just end the relationship.
If its an LDR, just end it. trust me.