If there is enough space arround I will not disturb them.

Being in zone 5, I cannot grow hippeastrum bulbs in the ground year 'round. If I could, I would probably treat these like any of my other perennials/bulbs that I do grow in beds, and divide them every 3 or 4 years, depending on how crowded they appeared. As Arif says, I wouldn't disturb them if they still have space to grow. If disturbed, it may throw off their bloom for a year. From your photo, it looks like the bulbs have plenty of growing room.

In container growing, the rule of thumb seems to be that division can take place when the babies/bulblets have a decent enough root system of their own. On the other hand, they look so nice blooming in clusters that I would hesitate to separate them unless they were too crowded in the pot.

jodik,

Thanks for your response! One question: "...the rule of thumb seems to be that division can take place"...
For container plants, is division *recommended* at that stage? Or just *possible*?

I would say division is possible when the babies have their own well-developed root systems and can support themselves. I would also say that it's not necessary, or necessarily recommended. Unless they are over-crowded in the pot, separation is a personal choice. If they are over-crowded, it might be a good idea to separate them in order to give them more growing room... this can mean simply giving them a larger pot, or separating them into individual pots... that choice would be up to you.

As Arif states, if they have plenty of growing room, it's better not to disturb them... this can disrupt their bloom schedule.