Nerd Pride Radio

Two best uses for a Bag of Holding for your party. Aiden, take notes.

Low level - Ring of Sustenance and your Gnome, Goblin or Halfling can hang out in that bag and get released with a standard action. That small Rogue or Sorcerer can be ready to wreak havoc at a moment's notice.

High Level - Flesh to Stone on one of your companions. That stone companion can hang out in that bag for as long as you see fit. A Dispel magic or Stone to Flesh and you can unleash said companion from that bag.

You could create a 'monster bag', but this will need a portable hole for a bigger monster. Dominate Monster on something useful, like say an Otyugh. Flesh to Stone that stone Otyugh. Mage Hand or invisibly put that hole where you want it to be. Dump the contents, then dispel your Stone to Flesh and Otyugh your opponents!

Would it be a suitable environment for dry-aging steaks?

Bard+Instrument+Life-Bubble+bag of holding=Awesome practice room

Is the passage of time the same in the bag as out?

There was a Knights of the Dinner Table series, Bag Wars, about how the group stored an army in a bag of holding that they planned to use to conquer a kingdom. Bad things happen, and the army ends up building a fortress in the bag to defend against the party, leading to a completely different war.

In the KotDT world, all interdimensional storage containers open a portal to a specific spot in another plane. If you enter the storage container yourself, you can travel between these areas. And if you put one interdimensional storage container into another, it causes the locations to randomly shift around, meaning you no longer can directly access what you put in either container. After they put the army in their bag of holding, they accidentally put another pouch of holding or something inside the bag, causing the shift. Not only did they lose the army, but all of their magic items they stored in there. They decided to go into “bag world” to track down their stuff. And by the time they tracked down where their stuff was, the army was pissed at being abandoned there, and had to scrounge other people’s bag of holding areas in order to survive. They had turned into a fortified pillaging army, and would not give back the parties’ magic items.