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I recently caught wind of a Poké Radar strategy where, if you catch a found Pokémon rather than knock it out, the next square will have an additional 10% chance to continue the chain (unless you refresh the Radar). That means the square four paces out will have a 98% chance of continuing the chain, so assuming you do things perfectly you will have a ~45% chance of reaching a chain of 40.
I'm not sure if that makes these little guys less valuable.