The short answer for a Tibetan Mastiff
Yes, a mature, well-socialised Tibetan Mastiff can generally be left during a normal workday, and independence is the main reason. Few breeds were shaped so completely for unsupervised judgement: these dogs guarded Himalayan camps and flocks through the night, deciding for themselves what counted as a threat. A settled adult typically sleeps through most of the day, conserving itself for the more watchful evening hours. That independence comes with conditions. Adolescent Mastiffs are powerful, slow to mature, and far more likely to test fences and chew structures, and no puppy of any giant breed should be left for a full day. Security, not loneliness, is the planning priority.
Independence cuts both ways
A Tibetan Mastiff does not usually pine in the way a devoted companion breed does, but a guardian left alone is still a guardian on duty. Every delivery, passer-by, and neighbouring dog may be assessed and announced, and this breed's bark carries. Barking that peaks at genuine events is the breed working; barking that runs for hours suggests frustration or an under-stimulating territory. Size raises the stakes of boredom. A frustrated young Mastiff can damage doors, dig under fencing, or climb in ways that surprise owners who assumed a heavy dog would not. The ancient instinct to roam, especially in an unneutered male sensing a female nearby, should never be underestimated.
Securing the Mastiff workday
Walk and check the boundary before this breed ever spends a day in it: fencing must be tall, sound, and dig-resistant, gates latched with something a clever, strong dog cannot nudge open. Provide a dry shelter, deep shade, and more water than you think necessary, in a vessel that cannot be tipped. Keep a morning routine of a calm walk and garden time, and tell neighbours and regular delivery drivers the dog is present, so nobody opens a gate carelessly. If a midday checker visits, it should be a person the Mastiff already accepts, briefed to read the dog's body language and never to force familiarity on a breed that reserves its trust carefully.
Reading the day from the dog
A coping Mastiff greets you with measured calm, has eaten and drunk normally, and shows a garden that looks as it did in the morning. Repeated escape attempts, a damaged gate, complaints about sustained night-style barking in daytime, or a dog who returns indoors wired rather than settled mean the territory or the routine needs work, not that the dog needs scolding. Increase morning exercise modestly, add large, durable occupation items sized for these jaws, and review what triggers the barking. A camera over the gate area often reveals the pattern within a few days, whether it is a particular dog walking past or simple frustration at a locked boundary.
Giants have their own limits
Senior Mastiffs and those with joint problems need easy access to a comfortable indoor resting place rather than a full day outside, and in hot weather this heavily coated breed must be able to retreat somewhere genuinely cool, since heat is a real danger to a dog built for mountain cold. During fireworks seasons or thunderstorms, even a stoic Mastiff is better checked on. Females in season and young males need containment reviewed honestly, not hopefully. With secure ground and a calm routine, the breed's self-reliance makes working life workable. KinsLe's Family Sharing puts your Mastiff's gate rules, accepted visitors, and daily routine in one shared profile, so every member of the household guards the details as carefully as the dog guards the house.