You are asking the wrong question. Your attendings are idiots. Like all medications, benzodiazepines are dosed by indication, taking into consideration individual differences in the patient, patient preferences, minimizing adverse effects, utilizing placebo effects, positive expectancy and so on. For example you could prescribe lorazepam TID, but it would not be unreasonable to prescribe it BID in a hypomanic or manic patient, or to prescribe it 5x/day in a catatonic patient. Valium would be prescribed qhs for insomnia, but is typically prescribed tid for anxiety, or for the excitement and hyperactivity that occurs when using the MAOIs (particularly parnate), and prescribed qid if scheduled for alcohol withdrawal (and then tapered down). Clonazepam can often be effectively prescribed once a day, particularly if you are using lower doses (such as 0.25 or 0.5mg) for insomnia or nighttime symptoms but it can also carry through the day. Alternatively it could be used BID or even TID.
Xanax is most commonly prescribed TID though xanni bars are asking to be used QID delicious as they. the correct method is never. there is never a reason to prescribe xanax. Alprazolam is not available on the NHS and somehow the UK hasn't fallen apart, but perhaps it would have treated their fears of immigration and prevented Brexit?
As clauswitz mentioned lipophilicity is important - this is why many psychiatrists don't like valium as it tends to cross the blood brain barrier quicker and work more rapidly and is thus more reinforcing than, say, clonazepam. lorazepam takes longer to work and its action is longer than the half-life would suggest. Rate of absorption is also important (diazepam and chlorazepate have a more rapid GI absorption than lorazepam or chlordiazepoxide). To a lesser extent, biotransformation is a factor - oxazepam, temazepam and lorazepam are conjugated rather than oxidized so are no prone to the whims and fancies of liver disease or ageing on drug metabolism.
Although temazepam is usually used for insomnia and thus prescribed qhs, there is no reason why it couldn't be used for other indications and given in divided doses
Also note that even long-half-life benzos have controlled release formulations because the regular ones often require multiple daily dosing (including valium)
Splik's rules for benzo prescription (adapted from George Orwell)
1. never prescribe Xanax
2. never use a short-acting benzo where a long-acting one will do
3. if it is possible to cut a benzo out (or lower the dose), always cut it out
4. never passively continue to prescribe benzos, when you can actively engage the patient in dose reduction and other more effective therapies
5. never prescribe benzos to patient who use DSM phrases, scientific words and jargon to convince you to prescribe them when a patient who was really mentally ill would use everyday English
6. Break any of these rules before doing anything outright barbarous