Many monks sit a 90-day retreat each year. Some monks sit two 90-day retreats a year (Zen). Some monks remain in mostly solitude and silence for years and decades.
So yes, although 10 days seems like a long time to somebody who is not used to silence and solitude (most of us in the West), it's a relatively short time to be alone and quiet. It just points out how insane our societal conditioning has made us.
If you want intense, you go to certain monasteries in Burma and Thailand where monks and laypeople are striving for liberation e.g. Panditarama Forest Monastery. Most Mahasi retreats are quite austere, and you can make it more challenging by not taking rest during the day, not lying down until time for bed, not spending much time in your residential quarters, etc.
But whatever the circumstances, if your health permits, don't quit! Meditation is meant to be time for one to face his demons, long suppressed, repressed, pushed away, hated, etc. I know over the last year or so, I have broken down maybe 100+ times into tears. It's all the stuff that's been stuck in our cells that have the chance to be released when our bodies become still, when we are not adding any experience purposefully through our sense doors. It's wonderful to cry and let go of some of the rigidity with which this culture imbues us.
Do Good, Avoid Evil, Purify the Mind.