If nothing is done relationships get boring after a while. To keep your relationship exciting you need to put in some work. As it is with everything in life everything you do not put effort in is bound to fail.
So, yes, relationship is expected to get boring after a while when no effort is put into making it exciting. To prevent this from happening, do little things that makes your partner feel special and keep him or her excited.
Relationships often lose their charm after a while. However, you need to keep the flame alive to prevent this from happening. They usually get boring because the partners stop trying to do the little things that pleased their spouses.
However, once you keep these small traditions alive, devote special attention to your relationship will not get boring. Instead, it will thrive as you achieve milestone after milestone. You see those old people with so much love in their relation. It is because they never compromised their relation. They always did the little things to make sure their spouse new they were special.