Here are some concrete numbers that I've pulled out of my butt but should give an idea of what you'll need to do in order for this strategy (liquidating your LEGO) to be effective. To sell a large lot like that quickly, what's the general consensus on the discount that will need to be applied? 20%-30%? I'm not sure if @diablo2112 would be willing to share the discount he gave to sell his lot quickly, but maybe just a rough estimate would suffice. He sold his collection pretty quickly, but what he was selling was also only a third of your value.
Let's assume a fictional mortgage amount of $200,000 (the end number doesn't much matter). And go through two selling scenarios... Selling your sets in bulk... One closer to the 20% discount and the other to the 30% discount.
ROUND 1 - NO SELLING OF LEGO
Mortgage $200,000, Interest 3% Monthly, 25 Years
YEARLY PAYMENTS: $11,381.07
MONTHLY PAYMENTS: $948.42
TOTAL PAYMENTS: $284,526.79
TOTAL INTEREST PAID: $84,526.79
ROUND 2 - SOLD ALL LEGO FOR $45,000 or approx 18.2% off total value
Mortgage $155,000, Interest 3% Monthly, 25 Years
YEARLY PAYMENTS: $8820.33
MONTHLY PAYMENTS: $735.03
TOTAL PAYMENTS: $220,508.26
TOTAL INTEREST PAID: $65,508.26
Investment Sold At $45,000
Total Loss $10,000
Total Savings On Mortgage Over 25 Years: $19,018.53
Effective Savings (mortgage savings - loss on value of sets): $9,018.53
Monthly Payments Are This Much Cheaper: $213.39
ROUND 3 - SOLD ALL LEGO FOR $40,000 or approx 27.3% off total value
Mortgage $160,000, Interest 3% Monthly, 25 Years
YEARLY PAYMENTS: $9104.86
MONTHLY PAYMENTS: $758.74
TOTAL PAYMENTS: $227,621.43
TOTAL INTEREST PAID: $67,621.43
Investment Sold At $40,000
Total Loss $15,000
Total Savings On Mortgage Over 25 Years: $16,905.36
Effective Savings (mortgage savings - loss on value of sets): $1,905.36
Monthly Payments Are This Much Cheaper: $189.68
My Conclusion ... I wouldn't liquidate your assets unless you can come close to that 20% discount.
Intangibles:
Your Buy-In: Of course we don't know your original buy-in so maybe the 55k is already 20-30% above your original investment and you're potentially breaking even.
What the Bank Will Give You: If you need to sell some in order to get a loan, by all means this may be a good strategy. Reducing your debt load is never a bad idea.
What You are Comfortable Paying: Some people only have so much tolerance for debt... And only so much money each month for the usual payments. Selling your LEGO will yield decent (not fantastic IMO) savings each month on your mortgage payments.
Important Note - I used a calculator that does monthly payments. Couldn't quickly find one that does bi-weekly... To improve your savings, I always recommend people use bi-weekly payments for their loan/mortgage repayments if offered by the bank. The interest savings and reduction in overall months you're paying down debt are substantial!!
(To the OP - I'm not assuming you haven't done this... I'm putting this out there for anyone who is reading your post and has never had a mortgage and is truly curious why opinions on this strategy and whether it may or may not work have been varied.)