Like so many questions about warfare that I've seen on this sub, the short answer to your question is "it depends."

Based on your question, I infer that you watched Band of Brothers, and I'll use that as a bit of reference. If you haven't watched the miniseries or read the book, I highly encourage you to do both.

Front line combat intensity is highly variable; a few hours on the front in a large battle could be far more dangerous than days or weeks in a quiet sector. An infantryman might shoot almost non-stop in a large battle, or barely at all other times, and BoB demonstrates this well. At Carentan, they shoot very frequently. Later on, when they were in Haguenau, they often rarely shot their weapons. During Market Garden and the Battle of the Bulge, they experienced long periods of relative inactivity punctuated by brief periods of extremely intense fighting. So not all 7 hours on the front are created equal.

Even these short periods of intense combat were rarely continuous. After all, combat is incredibly physically demanding, and there are physical limits that human beings reach which force them to slow down. If both sides reach this point and around the same time, there will likely be a temporary lull in the fighting. That's not to say that these lulls are safe - there may be artillery or mortar bombardment, and accompanying tanks may still continue to shoot - but the intensity would diminish.

But how can a single unit survive that long on the front? It doesn't really, not intact. Infantrymen take very, very high casualties in large-scale conventional wars. Looking at overall statistics is deceiving. Continuing to use the US as an example, about 3% of all American servicemen in WW2 became casualties (this includes wounded and missing, not just killed). But these casualties were not evenly distributed. Infantrymen accounted for only ~6% of all personnel in the US Army, yet suffered 80% of all Army casualties. Being an infantryman was, and continues to be, a dangerous business. Just during the Normandy campaign, E Company from BoB suffered just under 50% casualties. On a larger scale, the numbers are even scarier. The 4th Infantry Division was in combat for 299 days, from when it landed in Normandy on 6 June until the German surrender the following year. The division's paper strength was a little over 14,000 men (of which approximately half were actual infantrymen), and in that time, it suffered 22,454 battle casualties. That's approximately a 160% casualty rate, and about 80% of those casualties (~18,000) would be infantrymen. And 4ID was not a unique case, many American divisions suffered over a 100% casualty rate during the war.