What do they need to do, then? What action will constitute justification for taking another short rest? Is it based on the passage of time - you must spend two hours active before you can take another short rest? Or is it based on encounters - like 4E has mile-stones?
Whatever the DM feels like. Probably something that progresses the story somehow in a meaningful way. Rather than:
Party: okay we are ready to go.
Fighter: I still have ouchies beccause I have not used hit dice, curative magic, potions or whatever passes for healing in our world. I am going to spend 4 hours slowly using my extra fighter ability.
Party:
or
Party: let's head out
(Walks half a mile at a moderate pace)
Fighter: You know, I still have that crick in my neck. Let's take another short rest.
Party:
or
Party: Let's head out.
(Eventually finds and fights some goblins)
Fighter: Okay, I'm beat. Let's take another short rest.
Party: But we just took one before the goblins, and you did not take any damage!
Fighter: Yeah, well I'm still pretty beat from earlier. I just need a little nap.
Party:
The fighter in our party uses Second Wind once in a while when taking massive damage in combat. The rest of the time it does not really get used.
Really, it just comes down to a DM needing to intervene if having to deal with this being abused.
DM: You start to take a short rest only to discover there are signs of orcs in the area. Better press on.
Wizard: I cast
leomund's tiny hut.
DM: Everyone smells terrible in the cramped space. After a couple of minutes, you notice orcs gathering around the hut. The hut disappears as a shaman casts
dispel magic, and the orcs are upon you!
Second Wind does what its name says on the tin, provide a second wind. Not a third, fourth, and fifth wind.
Another option if it proves too problematic would be for the DM to eliminate Second Wind and give the fighter 1 more HP per level. The end result is about the same. There are a few HP less, but the HP is already there and does not require an action to activate.