The phrase "a variable period of" is correct and usable in written English.
It can be used when referring to a duration of time that can change or is not fixed.
Example: "The project will take a variable period of time to complete, depending on the resources available."
Alternatives: "an indeterminate duration of" or "a flexible timeframe of".
The child typically loses consciousness for a variable period of time.
Many clinicians advocate empiric bougienage, as patients will often report improvement of their dysphagia for a variable period of time after this is performed.
After a variable period of time, but usually within 5-years, most patients with abnormally low blood pressure on standing develop cognitive or motor abnormalities.
After infection, the disease usually follows a chronic course with a variable period of incubation extending from several weeks to several months.
The storage ring has a maximum energy of 1.5GeV and the OK is made of electromagnets with a variable period of 160 to 320mm.
After display, the birds land on a branch for a mating ritual which starts with locking bills, followed by the female hanging upside-down for a variable period of time, and then copulation while the male holds the female's neck.
Therefore, depending on when they entered the study, participants had to wait a variable period (a mean of 68 days) following the baseline assessment before the pre-treatment assessment was conducted.
Interestingly, following the onset of benign exertional headache, the attacks, occurring with a frequency of between one per day and one every 2 months, recurred over a very variable period of time usually lasting <20 years.
The start of natal dispersal in our population of golden eagles took place over a hugely variable period of time, with all individuals emigrating from their natal home range within their first year.
Most such diseases develop after a variable period during which that part of the nervous system subsequently affected apparently functions normally.
After a variable period (occult lymphedema), a series of events is initiated, culminating in chronic lymphedema.
