Most monsters don't take but maybe 10-15 minutes, tops. The flavor text takes most of that.
(The proofreading and going over it may takes months though, but by then its already posted ;P )
Btw, for those of you who love the old classics...
Huge Monsterous Humanoid (cold)
Hit Dice: 16d8+80 (152 HP)
Speed: 20 ft. (4 squares)
Armor Class: 15 (-2 dex, +9 natural, -2 size)
Base Attack/Grapple: +16/+33
Attack: Bite +13 melee (2d6+10)
Full attack: Bite +13 melee (2d6+9) and 2 slams +11 melee (1d6+9)
Space/Reach: 15 ft./15 ft.
Special Attacks: Killjoy, roar, swallow whole
Special Qualities: Bumble's bounce, immunity to cold, low-light vision, scent
Saves: Fort +12, Ref +8, Will +9
Abilities: Str 29, Dex 6, Con 21, Int 3, Wis 8, Cha 17
Skills: Listen +8, Spot +9
Feats: Diehard, Endurance, Great Fortitude, Multi-Attack, Power Attack, Snatch
Environment: Any cold land
Challenge Rating: 11
Alignment: Chaotic Neutral
Advancement: 17-23 HD (Huge), 24-36 HD (Gargantuan)
Level Adjustment: --
Artic terrors of the deep north, bumbles are a menace to those who wander far from Christmastown. Attracted to the home of Santa by the collective hatred of Christmas, bumbles would like nothing less than to tear it asunder. They are held in fear of the Fat Man himself however, and instead make raids and bring fear to those nearby.
A bumble appears almost as a giant, but is covered in a thick pelt of snow-white fur everywhere but its feet and hands. The skin beneath is an icy blue and as cold to the touch. Its face is beastial with huge round eyes above a sensitive nose, and below a gaping maw of sharp teeth complete with a long, rough tongue.
A bumble is a mixture of stealth and brazen boldness. It hides behind glaciers and large stones and leaps out upon its foes with its terrifying roar. It then boldy charges its prey, grabbing with its thick-skinned hands to shove them down its maw.
Bumble's Bounce (Ex):
Bumbles ignore the first fifty feet of a fall and takes only subdual damage from greater heights.
When witnessing anything to do with Christmas and other winter-time festivities the Bumble goes into an uproar similar to the barbarian’s rage (+4 Strength, +4 Constitution, +2 morale bonus on Will saves, –2 AC penalty). The furor lasts until the cause of its wrath is vanquished or removed from view, and the Bumble suffers no ill effects afterward.
A Bumble is unable to swim, sinking within 1 round when immersed.
As a free action every 1d4 rounds a bumble can unsettle those within 60 feet with a horrifying roar. A potentially affected creature that succeeds on a DC 21 Will save remains immune to the Bumble's roar for 24 hours. On a failure, creatures with 4 or less HD become panicked for 4d6 rounds and those with 5 or more HD become shaken for 4d6 rounds. The save DC is charisma based.
Swallow Whole (Ex):
A Bumble can try to swallow a snatched Medium or smaller opponent by making a successful grapple check.
A swallowed creature takes 2d8+8 points of bludgeoning damage and 8 points of acid damage per round from the bumble's stomach. A swallowed creature can cut its way out by using a light slashing or piercing weapon to deal 25 points of damage to the stomach (AC 14). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out.
A bumble’s stomach can hold 2 Medium, 8 Small, 32 Tiny, or 128 Diminutive or smaller opponents.