When you are in early stage (2nd stage), most of the time you are still able to work in the long run. The role of early stage cover is to payout a lump sum so that you can take a break from work and go through your treatment, both physically and emotionally.
Hence, i normally suggest the coverage is more or less your 6 months to 1 year income replacement.
3rd stage on the other hand normally will affect your ability to work (shorter working hours, or long MC for treatment). BUT, NOT NECESSARILY YOU WILL DIE WITHIN 5 YRS.
The payout is meant to replace your income loss, or even to cover alternative treatment like gene therapy or TCM oversea, that not covered under shield insurance.
More importantly, when you get sick, this payout enable you to full fill your life long dream.
Coverage for critical stage recommended to be 5 to 10 yrs annual income equivalent.
We are the same age, since your current sum assured is only $60k, you may consider getting a term to boast up the coverage.
For term, $500k for death/TPD + $250K Critical illness +$50K Early stage:
Monthly premium = $107
If you have budget can consider life : $300K death/TPD + $250K CI + $50K EarlyStage
Monthly Premium = $277
Cheers.