They work if you make them work. The question is whether you want a relationship that’s like a job or do you want to create a relationship you enjoy?
A long-distance relationship is just that, a relationship between people who are not physically together. If you enjoy your personal space by yourself, then it can be quite convenient. If you desire physical touch, then you may want to find alternatives. Also, you don’t own a relationship. You are merely spending the time of your life with another.
Despite the increased need for certainty, nobody knows how it will work out. Nobody needs to know neither. The only thing you can do is get clear on how you are feeling right now. If you are enjoying spending time with yourself and your separation is temporary, then all is fair. If the separation is lasting longer than you would like, reassess. Whatever you do, be always honest and open about your feelings and consider those of your partner.
Statistics can be fun to play with, but your relationship and your wellbeing are too special to base them on generalisations. The success of your relationship depends on your ability to trust your partner and being comfortable to share your feelings.
By telling them. In any relationship, there is a basic respect. In a long-distance relationship, it can be very tempting to just hang up to escape the unwanted feelings. Just remember, that this is the person you love and care about, so just consider their feelings before you act on your emotions.
Trust is taking a chance. You can increase your chances of being trusted by allowing her to open up and share her feelings without feeling judged.