While trying to carry out the above suggestions (don't worry if you can't manage all of them all of the time), you may still be wondering if you should be providing separate experiences for your multiples as a way of helping them develop individuality. There may be some benefit in arranged separations, but they needn't be forced before the twins are ready to accept them. If providing outings for one at a time imposes a great financial or logistical hardship on the family, try something simpler, like a five minute special talk-time with each child every morning or at bedtime.
In some families, each parent takes one twin on brief separate outings at the same time. Sometimes it works for one parent to take one out while the other twin stays home with the other parent. Few young twins understand this, however. They think the one staying home is being deprived or punished. A single parent who has a close relative or friend whom the children know well and are comfortable with might ask this person to babysit one child at a time to provide each one with some special private time with the parent.
Short periods away from a co-twin give each twin the opportunity to interact directly with an adult or other children, without help, interference or competition from each other. Especially in situations where one twin is more verbal and assertive and routinely expresses needs for the quieter twin, separate times call on a shy child to learn to "speak for yourself." Such experiences can be helpful for the development of language and a sense of individual social competence.