Assuming the plants in question are Mediterranean climate plants (ie. their habitat has a winter rainfall, summer drought climate) they should do very well with little or no summer water, provided temps don't get painfully hot in the summer. This would be Aeonium, Dudleya, a variety of plants from the west coast of South Africa, etc.
However, plants from other climates (eg. summer rainfall or tropical) may require some summer water to do well, depending very much on the plant and the situation. In all fairness xeric plants can often take a lot of summer drought if they are allowed to become established first. Your run of the mill agave or aloe will often deal very well with drought during any season, regardless of its climate of origin. I planted about 15 aloes and stopped watering after a year, and all of them survived our driest year on record, including an 8 month summer drought, regardless of whether they came from a winter rainfall climate.
There is definitely no reason to water more often or more deeply during winter, given that's when we get our rain. The average rainstorm here (not just a shower) will saturate the soil deeper and more evenly than it ever is when I water. Sure, if there's an extended period without rain, you might want to provide some water to keep plants looking good. But that's more like supplement to nature's goodness than a (poor) replacement for it (which summer irrigation would be in our climate).
One side note related to SoCal and NW BC local weather: we get some of our warmest and most of our driest days during winter (for example this past January we reached a couple degrees short of our annual high) due to the Santa Ana wind reversal events that take place at that time. (High) temperature and (low) humidity are big drivers for evaporation and transpiration, especially combined with wind. After 2 or 3 days with these conditions, the soil is very dry and plants tend to be beat up. The succulents look visibly deflated. So actually deep watering during winter makes a lot of sense if it occurs shortly after a Santa Ana event, especially when it hasn't rained for a while.
