All of this is based on observations, primarily by users here who have shared their first hand experience.
Galactic Readiness Decay seems to have multiple rates, depending on your readiness score, or perhaps on the source of the score.
In general, it appears to decay at a rate of 0.15% per hour or around 1% per 8 hours, or 3% per day to a minimum of 50%.
There have been some reports of up to 6% per day, though I haven't seen this number echoed elsewhere.
If your GR is low, between say 50-60% then it appears to slow the decay rate to around 1% per day.
It takes very little to beef this back up, if it is causing a problem for you. For example you can play multiplayer, by yourself, and complete the Geth mission ... it's fairly easy to achieve a bronze or silver victory.
As @Edwin notes, if you simply start and exit a game, it will not count as an active day. You have to finish the game, which is why I noted Bronze or Silver being fairly achievable on some missions.
Since this question was posted, the "Equipment Pack" has been replaced by the "Jumbo Equipment Pack" - basically the same thing but larger. Additionally, a variety of additional different packs have been added.
There are a large number of different equipment packs. In general, the packs available from the multiplayer store grant you items, weapons and powerups, and unlock character classes. Some packs have a focus on a particular type of item, so for example, an Arsenal Pack will have a greater focus on weapons while a Jumbo Equipment Pack will only drop powerups.
It is possible to unlock weapons and characters multiple times, and doing so will upgrade weapons or provide an experience bonus for the duplicate character unlocked.
The various types of equipment pack are as follows;
- Starter Pack - a free, single use pack, that unlocks weapons and characters
- Recruit Pack - unlocks basic weapons, mods, and characters. Includes 5 items with a small chance for an uncommon unlock
- Veteran Pack - unlocks more advanced weapons and mods. Includes 5 items with at least one uncommon item or better
- Spectre Pack - unlocks even higher quality gear, including 5 items or characters with at least 1 rare unlock or better
- Premium Spectre Pack - unlocks even higher quality gear, including 5 items or characters with at least 2 rares unlock or better
- Jumbo Equipment Pack - bonus equipment, includes 10 random equipment and supply items
- Arsenal Pack - Includes 5 random items with at least two rares or better, with a higher chance for weapon unlocks
- Reserves Pack - Includes 5 random items with at least two rares or better, with a higher chance for character unlocks
All packs available in the store (except the Starter Pack) can be purchased and used multiple times with both in game currency and Bioware points.
Additionally, there are a variety of promotional packs which were only available during exclusive events or through special offers:
- Battlefield 3 Pack - A bonus for having Battlefield 3 on your Origin account
- Premium Collectible Pack - A bonus for purchasing Mass Effect action figures
- Collector Rifle Pack - A bonus for preordering the art of the Mass Effect universe
- N7 Day Loyalty Pack - A gift from the Mass Effect team for playing on November 7th 2012
- Recruitment Reward Pack - A bonus for participating in the Mass Effect 3 Recruitment Program
- Vault Reinforcement Pack - A bonus for purchasing the Calibur11 Mass Effect 3 Vault console case
- Collectible Pack - A bonus for purchasing a physical copy of Mass Effect: Paragon Lost
- Gift Pack - A gift from the Mass Effect team
- Commendation Pack - A reward for completing an individual objective during an operation
- Victory Pack - A reward for the community completing the Community Goal during an operation
- Resurgence Pack
Best Answer
The "Premium Collectible Pack" comes with the purchase of action figure packs, as shown here.
The linked page describes the bonus in the following text:
This translates to the "special bonus for dedicated Mass Effect fans" you referred to in your question. It is misleading to have the word "free" included in any sort of description of this pack as you're required to spend a substantial amount to get the figures and code.
Referenced product: