Watering usually isn't a scheduled activity. It is "as the plants need it" and that need varies from climate to climate, week to week and age of the plants. Weather, soil amount and porosity, type of plant and stage of growth are only a few factors that can determine how often and how much one needs to water.

Tomatoes want consistent soil moisture levels. Lightly moist soil for best performance. So no, one would never let them dry out completely any more than one would flood the bed.

And daily watering tends to lead to shallow rooting and water dependent plants so while it might be needed during the very hottest and driest part of the summer, it also wouldn't be desirable on a regular basis either.

Raised beds tend to dry out faster than in-ground beds do but the type of soil will govern how fast they dry out. Not much help I know but I have some 18" raised beds that I use drip irrigation in. With my soil and in my mid-summer climate they require approx. 2 hours of 1 gph drip once a week if there has been no rain.

You will have to experiment with your soil and your set-up to determine how often and how much to water. Use your hands to dig down to the root level 6-8" down to determine how deep the surface water is moving and how fast it gets there.

Dave

I also have a raised bed that's 18" deep but it's made from composite lumber so it holds in the moisture better than wood lumber. I use a moisture meter to determine when to drip from my rain barrel. When the needle on the meter points to 4 or 5 (the scale is 1 through 10 with 4 being the beginning of the moist zone) I drip for a good hour at least or until the meter reads 7. The soil is considered wet from 8 and above. The link to the brand I have is below but there are scads of others as well. This one is pretty inexpensive and measures light levels as well as ph.

Here is a link that might be useful: Inexpensive moisture/light/ph meter

And yes, please do mulch on top of your drip lines. Mulch actually lessens soil born diseases from splashing up onto your plants. Mulch conserves water and cools the roots in hot weather. Pine straw, dried grass clippings, chopped dry leaves, clean straw, applied a few inches thick will benefit your plants, lessen your water bill and will improve the soil.

During the summer days, with no rain, I give each tomato plant about 2 gal. of water each time. My garden hose with a shower head delivers about 4pm. so say I have 6 plants in one bed, I water that bed for about 3-4 minutes, once every 5 to 7 days. I also have a rain gauge. Any rainfall less than 1/4 inch per week does not count. No watering when there is 1.5" of rain or more .