“He achieved another milestone.”
You hear such sort of statements after someone achieves something or someone succeeds in something. This something differs from person to person but the statement remains the same.
“And he is crossing milestones one after another.”
A question arises is why milestones only?? Do you know the reason??
Milestones are easy to get. You find them at every one mile distance. In international units its roughly 1.6 Km.When we achieve a milestone there is lot of hard work involved in it. We have the sweat dropping hours of work. Well the sweat dropping thing is not for the chefs and the ones related in food industry. You may get fired for dropping sweat there. 
The hard work we do cannot be compared to milestone. Milestones come every mile and they are easy to get. Unlike the success we get. It’s not everyday that we taste success. It’s a luxury. Comparing success to milestone is just not the respect and honor for the person’s work. Do you think success is like a milestone?? It always appears after every mile that we travel?? At least don’t include me in that list.
So what’s the alternative word for this? There is no perfect one. But I guess there’s a need to find for an English word. May be I am just not aware of the word. 
Till you reach another milestone…
Think Nonsense…